60 Annual Meeting Austrian Physical Society 6–10 September 2010

Transcription

60th Annual Meeting
Austrian Physical Society
6–10 September 2010
Salzburg, Austria
Faculty of Natural Sciences
University of Salzburg
Hellbrunnerstrasse 34, 5020 Salzburg, Austria
Impressum
Herausgeber:
Für die ÖPG
Maurizio Musso
Universität Salzburg
FB Materialforschung & Physik
Hellbrunnerstr. 34
A 5020 Salzburg
AUSTRIA
Tel: +43-662-8044-5525
Fax: +43-662-8044-150
E-mail: [email protected]
Layout:
Claudia Heissl
Druck:
Offset Druckerei 5020
EHRENSCHUTZ
Under the auspices of
Landshauptfrau
Mag. Gabi Burgstaller
Rektor der Paris Lodron Universität
O.Univ.-Prof. Dr. Heinrich Schmidinger
Vize-Rektor der Paris Lodron Universität
O.Univ.-Prof. Dr. Albert Duschl
Dekan der Naturwissenschaftlichen Fakultät
O.Univ.-Prof. Dr. Georg Amthauer
ORGANISATIONSKOMITEE
Organisation Committee
Ao.Univ.-Prof.
DI Dr. Maurizio Musso
Leitung und Organisation
Claudia Heissl
Tagungsbüro
Organisation
Tagungsband
Dr. Wilhelm Heidegger
EDV, Technik
DANKSAGUNG
Acknowledgements
Die Organisatoren danken für die freundliche Unterstützung von
The organizers wish to thank for the friendly support by
Bundesministerium für
Wissenschaft und Forschung
Bundesministerium für
Unterricht, Kunst, und Kultur
Land Salzburg
Stadt Salzburg
SPONSOREN / FIRMENAUSSTELLER
Sponsors / Industrial Exhibtion
INHALTSVERZEICHNIS
Table of Contents
1. Allgemeine Informationen / General Information
2. Programm / Program
3. Energietag (AKE)
4. teilchen.at Ausstellung / Exhibition
5. Hauptvorträge / Plenar Talks
6. Physik in Österreich – Physics in Austria
7. Preisvorträge / Prize Lectures
8. Fachtagungen / Topical Sessions
8.1. ACP
8.2 AKU
8.3 AMP
8.4 FAKT
8.5 FKP-NESY
8.6 GEP
8.7 LHS
8.8 MBU
8.9 OGD
9. Poster
9.1 AMP
9.2 FAKT
9.3 FKP
9.4 GEP
9.5 MBU
9.6 NESY
9.7 OGD
1
6
7
13
14
21
27
34
34
35
41
54
88
116
121
123
133
159
159
168
180
196
197
199
204
1. Allgemeine Informationen / General information
Die aktuellen Informationen können unter http://www.events.sbg.ac.at/oepg2010
abgerufen werden.
Die actual information can be downloaded from the conference website:
http://www.events.sbg.ac.at/oepg2010
Tagungsort / Conference Venue
Universität Salzburg, Naturwissenschaftliche Fakultät, Hellbrunnerstr. 34, A-5020
Salzburg, Austria.
University of Salzburg, Faculty of Natural Sciences, Hellbrunnerstr. 34, A-5020
Salzburg, Austria
Das Tagungsbüro befindet sich für die Dauer der Jahrestagung in der Naturwissenschaftlichen Fakultät beim Haupteingang.
The conference office is situated at the main entrance oft he Natural Sciences
Faculty for the duration of the conference.
Die Tagungsanmeldung ist über das Formular der Website:
http://www.events.sbg.ac.at/oepg2010/files/registration_form_engl_oepg_2010.pdf
oder auch direkt vor Ort im Tagungsbüro möglich.
The conference registration can be done via the registration form to be downloaded
from the website
http://www.events.sbg.ac.at/oepg2010/files/registration_form_engl_oepg_2010.pdf
or directly at the conference registration desk.
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Tagungsgebühren / Conference fees
Kategorie
ÖPG Mitglied und
assoz. Mitglied
Vor 31. Juli 2010
Nach 31 Juli 2010
Before 31 July 10
After 31 July 10
EURO 60
EURO 70
EURO 80
EURO 90
EURO 15
EURO 20
frei /free
EURO 15
frei/free
EURO 20
EURO 30
EURO 30
EURO 10
EURO 10
ÖPG Member and
assoc. Members
ÖPG Nicht-Mitglied
Non-Member
Lehrer
Teacher
Bachelor/Master
Student/Student
Doktorand/
PhD student
Tagesgebühr
Daily fee
Tagesgebühr
Doktorand
Daily fee
PhD-student
Anmeldung und Zahlungsmodalitäten / Registration and Payment
Vor der Konferenz / Before the conference:
Banküberweisung an / Bank transfer to
UniCredit Bank Austria AG (Rainerstr. 2, A-5020 Salzburg)
BLZ 12 000; Kto-Nr. 0695 3834 602; Universität Salzburg
IBAN AT23 1200 0069 5383 4602, BIC BKAUATWW
Referenzcode / Reference code: ÖPG 2010 ; Kostenstelle P_148500_03
Bei Tagungsrezeption: Es wird um Barzahlung ersucht. Die Anmeldung vor Ort
(siehe auch Tagungsprogramm) beginnt am Mo, 6. Sept. 10-16 Uhr, am Di, 7. Sept.
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von 09:00 bis 17:00 Uhr, am Mi, 8. Sept., und Do, 9. Sept. von 8:30 bis 16:30 Uhr
und am Fr, 10. Sept. von 8:30 bis 11 Uhr.
At the conference registration: You are kindly requested to pay in cash at the
registration. The registration times (see also program) are as follows: Mo, 6 Sept.
10hr00 to 16hr00, Tue, 7 Sept. 8hr30 – 16hr30, We, 8 Sept and Thu, 9 Sept from
8hr30 to 16hr30 and on Fr, 10 Sept from 8hr30 to 11hr00.
Reisekostenzuschuss für studentische ÖPG-Mitglieder
Travel support for student members of ÖPG:
Studentische ÖPG-Mitglieder können einen Reisekostenzuschuss mittels des im
Tagungsbüro aufliegenden Formulars beantragen (Befürwortung durch Betreuer
notwendig). Die Höhe der Zuschüsse richtet sich nach den zur Verfügung stehenden Mitteln, der Zahl der Ansuchen sowie der tatsächlichen Höhe der Reisekosten.
Student members of ÖPG can apply for travel support via the form available at the
registration. The signature (approval) of the applicants tutor is necessary on the
form. The amount of support depends of the funds available, the number of
applications and the actual travel costs.
Unterbringungsmöglichkeiten / Accommodation
Für die Stadt Salzburg können Unterkünfte beim Tourismusbüro Salzburg,
Tel.+43/662/88 98 7-0, Fax+43/662/88 98 7-32, E-mail: [email protected]
http://www.salzburg.com/tourismus/185.htm oder http://www.salzburg.info online
gesucht und gebucht werden.
For the City of Salzburg one can search / book via the Tourist Office Salzburg
Tel.+43/662/88 98 7-0, Fax+43/662/88 98 7-32, E-mail: [email protected]
http://www.salzburg.com/tourismus/185.htm oder http://www.salzburg.info online
Hörsäle und Ausstattung / Lecture rooms and equipment
Die Hauptvorträge, die Preisvorträge sowie die „Physik in Österreich“-Vorträge
finden im Audi Max (HS 401, Erdgeschoß) statt. Die Fachtagungen finden mit
Ausnahme der AKE und GEP (Haus der Natur, Museumsplatz 5; Bus Nr. 1 vom
Bahnhof und Bus Nr. 8 von der Naturwissenschaftl. Fakultät) im Erdgeschoß im
Blauen (HS 402) und im Grünen Hörsaal (HS 403), sowie im 1. Stock in den
Seminarräumen 411, 412, 414 und 415 statt.
Alle Hörsäle sind mit einem PC und einem Beamer ausgestattet, sodass die
Mitnahme eines USB-Sticks genügt. Betriebssystem ist MS Windows XP mit
PowerPoint als Standard-Präsentations-Software. Sollten Sie ein anderes Betriebs-
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system bzw. eine andere Präsentations-Software benötigen, so ist ein eigenes
Notebook mitzubringen. Technische Unterstützung vor Ort ist möglich.
Die Erfahrung zeigt, dass es bei den Beamer-Präsentationen immer wieder zu
zeitlichen Verzögerungen beim Ablauf der Sitzungen kommen kann (Inkompatibilitäten von Soft- & Hardware, Nicht-Standard-Schriftsätze, etc.). Für einen
reibungslosen Ablauf der Fachsitzungen sind die Fachausschuss-Vorsitzenden
verantwortlich.
The plenary talks, the prize lectures and the session “Physics in Austria” are
presented in the Audi Max (HS 401, ground floor). The topical sessions are
presented in Grüner und Blauer Hörsaal (HS 402 und HS 403, ground floor) and in
the lecture rooms 411, 412, 414 and 415 (first floor), with exception of the topical
sessions AKE and GEP which will take place at Haus der Natur (Museumsplatz 5;
reachable by bus no. 1 from the main station or bus no. 8 from the Faculty of
Natural Sciences).
All lecture rooms are equipped with computer and beamer for which you only need
to bring your USB-stick. Operating system is MS Windows XP with PowerPoint as
standard presentation software. Should you need another operation system resp.
another presentation software it is recommended to supply your own laptop.
Technical assistance will be available in the lecture rooms.
Experience has proved that there are always delays with preparation of lectures
due to incompatibility of software, etc. The chairmen and -women of the topical
sessions are responsible for the smooth operation of the session.
Posters
Format: Breite max. 97 cm, Höhe max. 147 cm, bzw. A0 Format. Posters können
bei Beginn der Tagung (Mo, 6. Sept. 2010) angebracht werden, und sollten
möglichst bis zum Abend des 9. Sept. 2010 ausgestellt bleiben. Bei der
allgemeinen Postersitzung am Di, 7. Sept. 2010, 15:30 Uhr, sollte mindestens ein
Autor beim Poster anwesend sein.
Format: Width: 97 cm, Height 147 cm (A0 Format). You can fix your poster on the
first of day of the conference (Mo, 6 Sept. 2010). On Tue,
7 Sept. 2010, at 15hr30 there should be at least one author presenting the poster at
the general poster session.
Internet-Zugang, E-mail / Access to Internet and E-Mail
Allen Tagungsteilnehmern stehen während der Tagung 10 PCs mit Internet-Zugang
im Trakt des Zentralen Informatikdienstes (Computerraum für Studierende; siehe
Plan) in der Zeit von 10 bis 18 Uhr zur Verfügung. Für die Nutzung dieser PCs wird
Username und Passwort an der Registration ausgegeben.
Zugang zum WLAN: Benutzer, die an ihrer Universität einen gültigen Account
haben, kommen sich automatisch in das WLAN der Universität Salzburg einwählen.
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Bei keinem gültigen Universitätsaccount können sich die Teilnehmer bei der
Registration einen Account holen (Username und Passwort).
There are 10 PCs with internet access available for all participants between
10hr00 – 18hr00 (guest computer room, 1st floor). Username and password for the
participants will be provided at the registration upon request.
For access to WLAN: For users with regular account at their home university
(valid for Europe and Canada) the WLAN of the University of Salzburg is
accessible. Users without regular account can request an account (i.e. username
and password) at the registration desk.
Buffet zur Postersession / Poster session buffet
Das Buffet wird am Di, 7. Sept. 2010 um 15 Uhr eröffnet parallel zur Poster-Session
und um 18 Uhr geschlossen.
The poster session buffet is open from 15hr00 to 18:00hr on Tuesday, 7 Sept 2010.
Übersichtsplan der Naturwissenschaftlichen Fakultät
Map of Natural Sciences Faculty
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2. Programm / Program
6
3. ENERGIETAG – Realisierung der Klimaziele
ENERGY DAY – Implementing the Climate Targets
Freier Eintritt – Free entrance
Montag – Monday, 6 September 2010 / Haus der Natur
Arbeitskreis Energie - Working Group Energy (AKE)
Parallel Session AKE
Zeit
Time
Vortragender
Lecturer
Vortragstitel
Title of Talk
14:00 - 14:10
Norbert Pillmayr
(Kelag)
Einleitung - Opening
14:10 - 14:50
Christian Kirchsteiger
(European Commission)
2020/2050 Perspectives
for Energy in the EU
14:50 - 15:30
Martin Greiner
(Aarhus University)
A 100% Renewable Energy
System for Europe
15:30 - 16:10
Helmuth Böck
(TU Wien)
Gibt es eine Renaissance
der Kernenergie?
16:10 - 16:30
Pause - Break
16:30 - 17:10
Christian Schwarz
(Kelag)
Generation Klimaschutz
17:10 - 17:50
Gudrun Weinwurm
(TU Wien)
Energie und Umwelt in der Forschung
17:50 - 18:30
Martin Thomas
(OMV)
OMV Gas & Power - Adapting to the
Changing Environment
Führung durch das Museum
Haus der Natur Guided Tour of the Museum
Haus der Natur
18:30 - 19:00
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AKE-1: Haus der Natur, Mo, 7. Sept, 14:10 Uhr
2020/2050 Perspectives for Energy in the EU
C. Kirchsteiger
European Commission, Directorate-General for Energy, Luxembourg
The objective of this presentation is to highlight the current and potential future roles
of energy in achieving the goals of the EU 2020/2050 energy and climate policy.
The relation between the achievement of these goals and the needs for further
decarbonisation of energy supply is evaluated in a 2050 perspective. It is shown
that the real issue is to strive for cost-effectiveness of solutions, involving both
decarbonisation and efficiency measures.
High shares of low-carbon electricity can be achieved in the EU by 2050 without
unreasonable costs while limiting fossil fuel dependency by applying on the demand
side measures related to energy efficiency, transport, co-generation, and on the
supply side measures related to the use of all low carbon options, i.e. renewables,
nuclear power plants, CCS and CO2 efficient fossil fuels.
Renewable energy and energy efficiency measures are by no means sufficient to
substitute for a phasing out of nuclear power plants.
In contrary, in order to achieve a sustained and secure electricity supply under the
constraints of the EU energy and climate policy goals, significant amounts of new
nuclear generating capacity need to be deployed in Europe over the next few
decades. An estimate of corresponding needs is given.
Finally, the European Commission’s actions towards creating an EU-wide
framework for a responsible use of nuclear energy are presented together with
current trends on both, EU and Member State levels.
A 100% Renewable Energy System for Europe
M. Greiner1, D. Heide1, L. von Bremen2 and C. Hoffmann3
1
Aarhus School of Engineering and Department for Mathematical Sciences,
Aarhus University, [email protected]
2
ForWind Center for Wind Energy Research, University of Oldenburg
Corporate Research and Technology, Siemens AG
3
The design of a 100% renewable energy system for future Europe depends on the
weather. The weather determines how much wind and solar power generation is
best for Europe, how much and what kinds of storage, balancing and power
transmission are needed, and how much cooperation between European countries
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is required. Simple spatio-temporal modelling, solid time-series analysis and the
physics of complex networks provide quantitative answers to these important
questions [1].
References
[1] Heide, D., Bremen, L., Greiner, M., Hoffmann, C., Speckmann, M.,
Bofinger, S., “Seasonal optimal mix of wind and solar power in a future,
highly renewable Europe”, Renewable Energy 35 (11), 2483-2489 (2010)
Gibt es eine Renaissance der Kernenergie?
H. Böck
Technische Universität Wien/Atominstitut, Stadionallee 2,1020 Wien
[email protected]
Am Ende der ersten Dekade des 21.Jahrhunderts zeichnet sich weltweit eine
beginnende Renaissance der Kernenergie ab. Diese ist einerseits gekennzeichnet
durch die Auswirkungen der Finanz– und Wirtschaftsprobleme und andererseits
durch die Entwicklungen der Klimaschutzdebatte, welche eine Dekarbonisierung
der Energie– und Industriestrukturen eingeleitet hat.
Die Produktion und Anwendung der Elektrizität spielt in diesem Zusammenhang
eine Schlüsselrolle, da auch in den nächsten Jahrzehnten mit steigendem
Elektrizitätsverbrauch in den Industrie-, Schwellen- und Entwicklungsländern zu
rechnen ist. Die Nutzung der Wasserkraft und der Kernenergie stellen derzeit die
bedeutendste CO2 freie Erzeugung von Elektrizität mit unterschiedlichen
Entwicklungen und Perspektiven dar. Österreich liegt gemeinsam mit Spanien und
Luxemburg an drittletzter Stelle bei der Erreichung des Kyoto-Zieles, das bis 2020
eine CO2 Reduktion von 20% gegenüber 1990 vorschreibt.
Seit etwa 10 Jahren zeichnet sich eine weltweite Renaissance der
Kernenergienutzung ab, obwohl dies von vielen NGO’s und Politikern aus
weltanschaulichen Gründen negiert wird. Wesentliche Aspekte dieser Renaissance
sind
x
bedeutende Laufzeitverlängerungen bestehender Anlagen in vielen
Ländern,
x
Revision der Nuklearpolitik (Ausstieg vom Ausstieg) in vielen europäischen
Ländern und
x
geplante bedeutende Investitionsprogramme in vielen Ländern Europas.
Ziel dieses Beitrages ist es, einen Überblick über den Stand und die zukünftige
Kernenergienutzung in Europa und insbesondere in den österreichischen
Nachbarstaaten zu geben. Der Fokus liegt dabei auf jenen Ländern in welchen es
in den letzten Jahren bedeutende Änderungen (Ausstieg vom Ausstieg,
Ausbauprogramme) in Sachen Kernenergienutzung gegeben hat.
Im europäischen Kontext kann Österreich daher nicht mehr als „Insel der NuklearSeligen“ bezeichnet werden, sondern wird zunehmend von Nachbarstaaten
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umrundet von denen Nuklearstrom importiert wird; der Anteil in Österreich wird
derzeit auf ca. 15% geschätzt. Durch den steigenden Stromimport erhöht sich der
Anteil an Nuklearstrom in Österreich weiter und wir werden zu einem ökologischen
Trittbrettfahrer Europas.
Generation Klimaschutz
C. Schwarz
KELAG – Kärntner Elektrizitäts-AG, Arnulfplatz 2, 9020 Klagenfurt
[email protected]
Der Energiesektor steht im Spannungsfeld der Zielvorstellungen des Energie- und
Klimapakets der EU, der daraus abgeleiteten landesspezifischen Gesetzgebung
und einem stetig steigenden Energiebedarf. Darüber hinaus nimmt die
Sensibilisierung der Bevölkerung für Klimaaspekte permanent zu.
Der Vortrag widmet sich nun der Thematik, wie sich die Kelag als
Landesenergieversorger und internationaler Energiekonzern diesen Herausforderungen stellt. Es wird ausgehend von einer kurzen Darstellung der
Rahmenbedingungen die Strategie der Kelag und deren Entwicklung bzw. die darin
enthaltenen Maßnahmenschwerpunkte vorgestellt.
Einen wesentlichen Bestandteil zur Umsetzung der Strategie stellt die Kampagne
„Generation Klimaschutz“ dar, weshalb auf diese im Besonderen eingegangen wird.
Mit der Kampagne „Generation Klimaschutz“ verfolgt die Kelag das Ziel, das
Bewusstsein ihrer Kunden für Klimaschutz und Energieeffizienz zu schärfen, um
ihrer hohen Verantwortung nachzukommen.
Energie & Umwelt in der Forschung
G. Weinwurm1, S. Seidler2 und B. Neunteufl3
1,2
Technische Universität Wien, Vizerektorat für Forschung,
1040 Wien, Karlsplatz 13, [email protected]
3
Technische Universität Wien, Büro für Öffentlichkeitsarbeit,
1040 Wien, Operngasse 11
Das Wachstum der Weltbevölkerung und die zunehmende Globalisierung – und
dadurch auch Industrialisierung – werden zu einer Verdoppelung des Primärenergiebedarfs bis zum Jahr 2050 führen. Der vermehrte Einsatz von fossilen
Ressourcen (Kohle, Öl und Gas) ist einerseits wegen der begrenzten Reserven mit
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Risiken bei der gesicherten und preisstabilen Beschaffung verbunden, andererseits
mit Klima- und Umweltauswirkungen wie Erderwärmung und Luftverschmutzung.
Bei der Lösung dieses Konfliktes werden traditionelle technologische Lösungsansätze immer stärker versagen, die auf einer Effizienzsteigerung von bekannten
Energieumwandlungstechnologien und auf Methoden und Verfahren zur rascheren
Erschließung von zusätzlichen (fossilen) Ressourcen beruhen. Die Betrachtung der
gesamten Energiewandlungskette und der Technologie-lebenszyklen in ihrer
Effizienz, ihren Kosten und ihren Umweltauswirkungen wird genauso erforderlich
sein wie die stärkere Orientierung in Richtung nachhaltiger Technologien.
Unter diesen Gesichtspunkten erfolgte eine Neuorientierung der Energieforschung
an der Technischen Universität Wien. Der Forschungsschwerpunkt Energie und
Umwelt verfolgt einen systemtechnischen und interdisziplinären Ansatz, bei dem
die breiten technologischen Kompetenzen der TU Wien im Energiebereich durch
interne wissenschaftliche Expertise in den Bereichen Klima, Umwelt, Wirtschaft und
Ressourcen erweitert werden. Getreu dem Mission Statement der TU Wien
„Technik für Menschen“ können dadurch für die bedeutenden lokalen und globalen
Zukunftsfragen an Forschung, Wirtschaft und Gesellschaft genauso ganzheitliche
Lösungen erarbeitet werden wie für komplexe interdisziplinäre Forschungsaufgaben.
Aufbauend auf der an der TU Wien vorhandenen Kompetenz wurden sechs
wesentliche Forschungsgebiete zum Thema Energie und Umwelt identifiziert:
„energieaktive Siedlungen und Infrastrukturen“, „nachhaltige und emissionsarme
Mobilität“, „klimaneutrale Energieerzeugung, -speicherung und -verteilung“,
„Umwelt-Monitoring und Klimaanpassung“, „effiziente Nutzung von stofflichen
Ressourcen“, „nachhaltige Technologien, Produkte und Produktion“.
Um die Vernetzung und den Informationsaustausch zwischen den
Forschungsgruppen an der TU Wien zu erweitern, wurde das virtuelle
Forschungszentrum „Energie und Umwelt“ gegründet, das unbehindert durch
organisatorische Grenzen wie Institute oder Fakultäten aufgestellt, als offenes
Netzwerk organisiert und in einem zentralen Managementknoten gebündelt ist. Es
dient als Kommunikations- und Projektplattform für die ForscherInnen der TU Wien,
um neue Ideen und Zusammenarbeiten im Rahmen von innovativen
interdisziplinären Projekten zu ermöglichen und fakultätsübergreifende Lösungen
zu erarbeiten. Durch diese Initiative ist eine stärkere Nutzung von Synergien zu
erwarten, sowie eine erhöhte Aufmerksamkeit von Öffentlichkeit und Förder- und
Auftraggebern in Bezug auf die Kompetenzen der TU Wien.
Selbstverständlich und notwendig ist auch die Offenheit und Kooperationsbereitschaft nach außen. Im Rahmen des Forschungsschwerpunktes erfolgen der
Ausbau und eine Verstärkung der Kooperationen mit anderen österreichischen
Universitäten, sowie der Ausbau der Kooperation mit Wirtschaft und Körperschaften
und eine Internationalisierung der Forschung.
11
OMV Gas & Power – Adapting to the Changing Environment
M. Thomas
OMV Power International GmbH, Trabrennstrasse 6-8,
1020 Wien, [email protected]
The energy market environment is currently changing, long term growth of gas and
power is expected. Key drivers for this assumption is further electrification, CO2
regulations and increased liquidity of gas and power markets.
Power generation in OECD Europe drives the gas demand increase. European
import dependency shapes the gas infrastructure development as Europe is the
largest net gas importer, domestic production is decreasing and the link between
Southeastern and Caspian supply regions will increase flexibility.
OMV is adapting its business portfolio based on the changing energy map.
Creation of energy hubs, new development of combining CO2 capture technologies
with EOR and EGR, and strengthening E&P and Gas&Power in terms of
investments will change the portfolio. On top, OMV invests in gas fired and
renewable power generation assets.
Conversion from gas to power enables the optimization of gas and power assets
in OMV’s core markets. Building up a balanced portfolio of power plants in terms of
fuel and markets will create additional value to OMV and a reduction of the CO2
footprint.
The flexibility of gas fired power plants and renewable assets fit well together.
Overview on the status quo of OMV’s power plant projects: CCPP Brazi/Romania,
CCPP Samsun/Turkey, CCPP Haiming/Germany, windpower Dorobantu/Romania,
Heat Recovery Plant Weitendorf/Austria.
12
4. teilchen.at EXHIBITION
Ausstellungsdauer / duration of exhibition:
3 bis 20 September 2010
Mo - Fr 8:30 – 18:30
Ausstellungsort / Location:
Foyer der Naturwissenschaftlichen Fakultät, Universität Salzburg
Hellbrunnerstrasse 34, A 5020 Salzburg
Freier Eintritt – free entrance
http://events.teilchen.at
Moderne Grundlagenforschung aus dem Bereich Sterne.Kerne.Teilchen
mit Fokus auf österreichische Beiträge und ihre Anwendungen sind Thema
der „teilchen.at“ Ausstellungen.
Subject of the exhibition “teilchen.at” is modern fundamental research
around the topic Stars.Nuclei.Particles, focused on Austrian contributions
and related applications.
13
5. HAUPTVORTRÄGE / PLENARY TALKS
Dienstag - Tuesday 7 September 2010 / Audi Max
Plenarvorträge - Plenary Talks
Zeit
Time
Vortragender
Lecturer
Vortragstitel
Title of Lecture
10:30 11:30
Reinhard Kienberger
(MPQ Garching)
Attosecond Physics - From generation
of attosecond pulses to applications
on solids
11:30 12:30
Rupert Ursin
(IQOQI Wien)
Entangled photons
Öffentlicher Vortrag - Public Lecture
18:30 20:00
Rudi Grimm
(IQOQI Innsbruck)
Cool und faszinierend:
Quantenmaterie am absoluten Nullpunkt
Mittwoch - Wednesday 8 September 2010 / Audi Max
Zeit
Time
Vortragender
Lecturer
Vortragstitel
Title of Lecture
9:00 10:00
Harald Giessen
(Univ. Stuttgart)
Three-dimensional metallic
metamaterials:
From simple to complex –
coupling matters!
10:00 11:00
Osamu Kumagai
(Sony Corporation)
Physics in Industry, 50 Years
of laser innovation of laser diode
and optical storage
14
Donnerstag - Thursday 9 September 2010 / Audi Max
Zeit
Time
Vortragender
Lecturer
Vortragstitel
Title of Lecture
11:30 12:30
Steven T. Bramwell
(University College London)
Magnetricity and magnetic
monopoles in spin ice
18:30 20:00
Sterne - Kerne – Teilchen:
Eine Reise von den kleinsten
Teilchen bis zu den Grenzen
des Weltalls auf der Suche
nach der neuen Physik
Robert Schöfbeck
(HEPHY, ÖAW)
15
PVH-1: Audi Max, Di, 7. Sept, 10:30 Uhr
Attosecond Physics - From Generation of Attosecond Pulses to
Applications on Solids
R. Kienberger
Max-Planck-Insitut für Quantenoptik, Garching, Germany
The generation of ever shorter pulses is a key to exploring the dynamic behavior of
matter on ever shorter time scales. Over the past decade novel ultrafast optical
technologies have pushed the duration of laser pulses close to its natural limit, to
the wave cycle, which lasts somewhat longer than one femtosecond (1 fs = 10-15 s)
in the visible spectral range. Time-resolved measurements with these pulses are
able to trace atomic motion in molecules and related chemical processes. However,
electronic dynamics inside atoms often evolve on an attosecond (1 as = 10-18 s)
timescale and require sub-femtosecond pulses for capturing them.
Atoms exposed to a few oscillation cycles of intense visible or near-infrared light are
able to emit a single electron and XUV photon wavepacket of sub-femtosecond
duration [1,2]. Precise control of these sub-femtosecond wavepackets have been
achieved by full control of the electromagnetic field in few-cycle light pulses [3].
These XUV pulses together with the few-cycle (few-femtosecond) laser pulses used
for their generation have opened the way to the development of a technique for
attosecond sampling of electrons ejected from atoms or molecules [4]. This is
accomplished by probing electron emission with the oscillating electric field of the
few-cycle laser pulse following excitation of the atom by the synchronized subfemtosecond XUV pulse. Sampling the emission of photo electrons in this manner
allows time-resolved measurement of the XUV pulse duration as well as of the laser
field oscillations [5].
After the full characterization of these tools, first experiments have been carried out
to measure sub-femtosecond behavior of matter. Recently, the dynamics of the
photoionization process on solids has been studied [6]. Not only that attosecond
metrology now enables clocking on surface dynamics, but also the individual
behaviour of electrons of different type (core electrons vs. conduction band
electrons) can be resolved. Here, we measured a time delay of about 100 as on the
emission of the aforemention two types of electrons. The information gained in
these experiments may have influence on the development of many modern
technologies including semiconductor and molecular electronics, optoelectronics,
information processing, photovoltaics, electrochemical reactions, electronically
stimulated chemistry on surfaces and interfaces, non-adiabatic reactions, optical
nano-structuring, and interference effects in spectroscopy.
References
[1]
M. Hentschel et al., Nature 2001, 414, 501.
[2]
R. Kienberger et al., Science 2002, 297, 1144.
[3]
A. Baltuska et al., Nature 2003, 421, 611.
[4]
R. Kienberger et al., Nature 2004, 427, 817.
[5]
E. Goulielmakis et al. Science 2004, 305, 1267.
[6]
A. Cavalieri et al., Nature 2007, 449, 1029.
16
PVH-2: Audi Max, Di, 7. Sept., 11:30 Uhr
Entangled Photons
R. Ursin
Institute for Quantum Optics and Quantum Information (IQOQI)
Austrian Academy of Science, Vienna, Austria
It is an open issue whether quantum laws, originally established to describe nature
at the microscopic level of atoms are also valid in the macroscopic domain on
distances accessible in space. Some proposals predict that quantum entanglement
is limited to certain mass and length scales or altered under specific gravitational
circumstances. Testing the quantum correlations over distances achievable with
systems placed in the Earth orbit or even beyond would allow to verify both, the
validity of quantum physics and the preservation of entanglement over distances
impossible to achieve on ground. Another area of applications is in metrology where
quantum clock synchronization and quantum positioning are studied. We proposed
to the European Space Agency (ESA) to perform space-to-ground quantum
communication tests from the International Space Station (ISS) orbiting at a height
of approximately 400 km. We present the proposed experiments in space as well as
the design of a space based quantum communication payload. Additionally we will
present the ongoing ESA funded R&D activities performed in a consortium
consisting of partners from academia as well as from industry.
PVH-3: Audi Max, Di, 7. Sept., 18:30 Uhr
Public Lecture: Free entrance
R. Grimm
Institut für Experimentalphysik, Universität Innsbruck und
Institut für Quantenoptik und Quanteninformation (IQOQI),
Österreichische Akademie der Wissenschaften, Innsbruck, Austria
[email protected]
Richtig "heiß" geht es in der Quantenwelt gerade dann zu, wenn es extrem kalt
wird. Bei Temperaturen von nur wenigen Milliardstel Graden über dem absoluten
Nullpunkt zeigen kleine Atomwolken ein sehr eigentümliches Verhalten. Es
entstehen Quantenkondensate, in denen sich Millionen einzelner Teilchen völlig
gleich verhalten. Eine merkwürdige Zweiklassengesellschaft tritt in Erscheinung,
wobei einige Atome sich besonders gesellig benehmen, andere Atome aber zu
Einzelgängern werden. So bizarr dieses Verhalten auch erscheint, liefert es einen
17
Schlüssel zum tieferen Verständnis von Materie sowie die Grundlage für neue
Anwendungen. Vor allem aber ist es faszinierend, verblüffend und einfach cool.
PVH-4: Audi Max, Mi, 8 Sept., 09:00 Uhr
Three-Dimensional Metallic Metamaterials:
From Simple to Complex – Coupling Matters!
H. Giessen
4th Physics Institute and Research Center SCOPE, University of Stuttgart,
Germany
Metallic metamaterials have shown a number of fascinating properties over the last
few years. A negative refractive index, negative refraction, superlenses, and optical
cloaking are some of the ambitious applications where metamaterials hold great
promise. We are going to present fabrication methods for the manufacturing of 3D
metamaterials [1]. We are investigating their coupling properties and the resulting
optical spectra. Hybridization of the electric [2] as well as the magnetic [3]
resonances allows us to easily understand the complex optical properties. Lateral
as well as vertical coupling can result in EIT-like phenomena [4,5,6]. These
phenomena allow construction of novel localized surface plasmon resonance
sensors with a figure of merit as high as five [7]. The connection between structural
symmetry and their electric as well as magnetic dipole and higher-order multipole
coupling will be elucidated. It turns out that stereometamaterials [8], where the
spatial arrangement of the constituents is varied, reveal a highly complex rotational
dispersion.
References
[1]
Na Liu, Hongcang Guo, Liwei Fu, Stefan Kaiser, Heinz Schweizer, and
Harald Giessen:
Three-dimensional photonic metamaterials at optical frequencies,
Nature Materials 7, 31 (2008).
[2]
N. Liu, H. Guo, L. Fu, S. Kaiser, H. Schweizer, and H. Giessen:
Plasmon Hybridization in Stacked Cut-Wire Metamaterials,
Advanced Materials 19, 3628 (2007)
[3]
Na Liu, Liwei Fu, Stefan Kaiser, Heinz Schweizer, and Harald Giessen:
Plasmonic Building Blocks for Magnetic Molecules in Three-Dimensional
Optical Metamaterials, Advanced Materials 20, 3859 (2008).
[4]
Na Liu, Stefan Kaiser, and Harald Giessen:
Magnetoinductive and Electroinductive Coupling in Plasmonic Metamaterial
Molecules,
Advanced Materials 20, 4521 (2008).
[5]
Na Liu, N. Liu, L. Langguth, T. Weiss, J. Kästel, M. Fleischhauer, T. Pfau,
and H. Giessen: Plasmonic EIT analog at the Drude damping limit
Nature Materials 8, 758 (2009).
18
[6]
[7]
[8]
B. Lukyanchuk, N.I. Zheludev, S.A. Maier, N.J. Halas, P. Nordlander,
H. Giessen, and C.T. Chong:
The Fano resonance in plasmonic nanostructures and metamaterials,
Nature Materials 9 (2010), in press.
Na Liu, T. Weiss, M. Mesch, L. Langguth, U. Eigenthaler, M. Hirschner,
C. Sönnichsen, and H. Giessen:
Planar metamaterial analog of electromagnetically induced transparency for
plasmonic sensing
Nano Lett. 10, 1103 (2010).
Na Liu, Hui Liu, Shining Zhu, and Harald Giessen: Stereometamaterials
Nature Photonics 3, 157 (2009).
PVH-5: Audi Max, Mi, 8 Sept., 10:00 Uhr
Physics in Industry, 50 Years of Laser Innovation of Laser Diode and
Optical Storage
O. Kumagai
Sony Corporation Japan
Laser Diode is always in the heart of optical storage systems and a variety of other
industrial applications. Innovations in Laser Diode technologies have brought
optical storage evolutions from CD, to DVD and then BD in every 10 years.
Reviewing the development history would tell us how physics has created a huge
market and why recent innovations will predict future applications.
PVH-6: Audi Max, Do 9 Sept., 10:30 Uhr
Magnetricity and Magnetic Monopoles in Spin Ice
S. T. Bramwell
London Centre for Nanotechnology, University College London, UK
In the absence of electrical currents Maxwell's Laws imply that magnetic
phenomena can be represented in terms of magnetic charge or pole density.
A consequence of this is that the ends of long thin bar magnets attract each other
by Coulomb's Law, as discovered by Coulomb himself in the mid 19th century. So if
magnetic poles can behave like electrical charges, can they form a magnetic
equivalent of electricity - "magnetricity"?
The conventional answer to this question is no, because magnetic charge in
materials remains essentially dipolar as opposed to being free to move
19
independently as monopoles. The independent motion of magnetic monopoles is a
prerequisite for magnetricity.
In this talk I shall describe recent experiments that prove that some real materials
do contain magnetic charge in the form of freely moving, emergent magnetic
monopoles - atom sized packets of magnetic charge that may form currents
analogous to electrical currents. This remarkable phenomenon occurs in a class of
material called "spin ice". I will show how the conduction of magnetic charges in
spin ice is equivalent to the conduction of electric charge in weak electrolytes such
as water or water ice, and I will demonstrate how this analogy enabled us to
quantitatively measure the elementary magnetic charge [1].
[1] Bramwell et al., Nature 461, 956 (2009).
PVH-7: Audi Max, Do, 9 Sept., 18:30 Uhr
Public Lecture: Free entrance
Sterne – Kerne – Teilchen
Eine Reise von den kleinsten Teilchen bis zu den Grenzen des Weltalls
auf der Suche nach der neuen Physik
R. Schönbeck
Institut für Hochenergiephysik, Österreichische Akademie der Wissenschaften,
Vienna, Austria
Wir begeben uns zuerst auf eine bildhafte Reise zu den riesigen kosmischen
Strukturen im Weltall, welche die moderne Physik seit kurzem vor schwierige Rätsel
stellt. Auf der Suche nach der Zusammensetzung des Universums müssen wir auch
in die Welt der Elementarteilchen eindringen an der man sieht, wie neueste
Erkenntnisse über die kosmische dunklen Materie wichtige Impulse für Experimente
am großen Teilchenbeschleuniger, dem LHC am CERN in Genf, liefern. Danach
sehen wir uns an, wie die Experimente der Teilchenphysiker ablaufen, welche
Technik hinter den gewaltigen Anlagen steht und wie das alles mit den großen
Fragen der Kosmologie zusammenhängt.
20
6. PHYSIK IN ÖSTERREICH / PHYSICS IN AUSTRIA
Dienstag - Tuesday 7 September 2010 / Audi Max
Physik in Österreich - Physics in Austria
Zeit
Time
Vortragender
Lecturer
Vortragstitel
Title of Lecture
Fachausschuss Oberflächen, Grenzflächen, Dünne Schichten Scientific Committee Surfaces, Interfaces, and Thin Layers (OGD)
13:30 13:50
Peter Puschnig
(MU Leoben)
Imaging molecular orbitals through
photoemission spectroscopy
Fachausschuss Kern- und Teilchenphysik Scientific Committee Nuclear and Particle Physics (FAKT)
13:50 - 14:10
Victor-Franz-Hess Prize Lecture:
High precision flavor physics
at the Belle experiment
Wolfgang Dungel
(HEPHY ÖAW)
Fachausschuss Forschung mit Neutronen und Synchrotronstrahlung Scientific Committee Research with Neutrons and Synchrotron Radiation
(NESY)
14:10 - 14:30
Oskar Paris
(MU Leoben)
Physics of fluids in confined geometries
Fachausschuss Festkörperphysik –
Scientific Committee Solid State Physics (FKP)
14:30 - 14:50
Femto-second spectroscopy:
Measuring the beat of a quantum
cascade laser
Wolfgang Parz
(TU Wien)
21
Fachausschuss Geschichte der Physik
Scientific Committee History of Physics (GEP)
Franz Sachslehner
(Univ. Wien)
14:50 - 15:10
Historisch wertvolle physikalische
Peter Maria Schuster
Instrumente im Europäischen Zentrum für
(Victor-Franz-HessPhysikgeschichte „echophysics“ in Schloss
Gesellschaft)
Pöllau: eine Auswahl aus den Altbeständen
der Fakultät für Physik der Universität Wien
Brigitte Strohmaier
(Univ. Wien)
PA-OGD-1: Audi Max, Di, 7 Sept, 13:30 Uhr
Imaging Molecular Orbitals through Photoemission Spectroscopy
P. Puschnig1, S. Berkebile2, A. J. Fleming2, G. Koller2,
C. Ambrosch-Draxl1, F. P. Netzer2 and M. G. Ramsey2
1
Lehrstuhl für Atomistic Modelling and Design of Materials, Montanuniversität
Leoben, Franz-Josef-Straße 18, 8700 Leoben,
2
Institut für Physik, Karl-Franzens-Universität Graz, Universitätsplatz 5, 8010 Graz
Angle-resolved photoemission spectroscopy (ARPES) is commonly applied to study
the band structure of solids by measuring the kinetic energy versus angular
distribution of the photo-emitted electrons. Here we apply this experimental
technique to characterize discrete orbitals of large -conjugated molecules. By
evaluating the transition matrix element of the ultra-violet photoemission process,
we are able to establish a simple relation between the observed angular intensity
distribution and the Fourier transform of the initial state orbital. Thus, by measuring
two-dimensional photoemission intensity maps at constant initial state energy, we
are able to reconstruct the real space electron distribution of individual molecular
orbitals [1,2]. We apply the technique to a crystalline film of pentacene and a highlyoriented monolayer of para-sexiphenyl adsorbed on Cu(110). The data allows us to
precisely determine the molecular orientation and to image the HOMO and LUMO
orbitals, respectively. Given recent advances in ARPES instrumentation, we believe
the demonstrated simple relation between the photoemission intensity and the
22
Fourier transform of the molecular orbital can be a valuable tool for further
investigation of organic molecular films and monolayers. Moreover, we anticipate
that reciprocal space maps from ARPES experiments could nicely complement
scanning probe techniques in continued attempts to image individual molecular
wave functions [3].
References
[1]
P. Puschnig et al. “Reconstruction of Molecular Orbital Densities from
Photoemission Data”, Science 326, 702-706 (2009)
[2]
J. Ziroff et al.,“Hybridization of Organic Molecular Orbitals with Substrate
States at Interfaces: PTCDA on Silver“, Phys. Rev. Lett. 104, 233004 (2010)
[3]
F. Himpsel, “Angle-resolved photoemission: From reciprocal space to real
space“, J. Electron. Spectrosc. Relat. Phenom.
doi:10.1016/j.elspec.2010.03.007 (2010).
PA-FAKT-2: Audi Max, Di, 7 Sept, 13:50 Uhr
Victor-Franz-Hess Prize Lecture
High Precision Flavor Physics at the Belle Experiment
W. Dungel
Institut für Hochphysik, Österr. Akademie der Wisenschaften
Nikolsdorfergasse 18, A 1040 Wien
[email protected]
The Belle experiment in Tsukuba, Japan, has collected a data sample of close to
1.6 billion B meson decays which allows to study differences in the decays of
particles and anti-particles with high precision. This matter-antimatter asymmetry,
called "CP violation", is a necessary condition for baryogenesis, the process
thought to be responsible for the matter dominance in the universe. Belle's
observations confirmed the theory of CP violation by M. Kobayashi and
T. Maskawa, leading to their Nobelprize in Physics in 2008.
In my presentation, I will summarize some of the achievements of the Belle
experiment and introduce the future Belle-II upgrade. Furthermore, I will describe
how I contributed to the study of CP violation through a high precision measurement
of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb|.
23
PA-NESY-3: Audi Max, Di, 7 Sept, 14:10 Uhr
Physics of Fluids in Confined Geometry
O. Paris
Institute of Physics, University of Leoben
Franz-Josef-Straße 18, 8700 Leoben Austria
Email: [email protected]
Nanoporous materials with cylindrical pores of some nanometers in diameter on a
highly ordered pore lattice are ideal model systems to study the behaviour of fluids
in confinement. We employed small-angle neutron scattering (SANS) and
synchrotron radiation based small angle X-ray scattering (SAXS) to study liquid film
formation and gas-liquid phase transitions (capillary condensation) of simple fluids
[1], water [2], and the self assembly of amphiphilic molecules [3]. We also
investigated the interaction of the guest fluids with the host solid pore walls, which
leads to a fluid pressure dependent deformation of the solid material [4]. This
deformation can be monitored in-situ by following the shift of the Bragg reflections
from the pore lattice and allows extracting nanomechanical properties of the
material [5]. The basic physics of the adsorption induced deformation can be
understood by combining fundamental principles of fluid thermodynamics with solid
mechanics [5,6].
References
[1]
Findenegg, G.H., Jähnert, S., Müter, D., Prass J. and Paris O., “Fluid
adsorption in ordered mesoporous solids determined by in-situ small-angle
X-ray scattering”, Phys. Chem. Chem. Phys. 12, 7211-7220 (2010).
[2]
Erko, M., Wallacher, D., Brandt, A. and Paris, O., In-situ Small-Angle
Neutron Scattering Study of Pore Filling and Pore Emptying in Ordered
Mesoporous Silica, J. Appl. Cryst. 43, 1-7 (2010).
[3]
Mueter, D., Shin, T., Deme, B., Fratzl, P., Paris O. and Findenegg, G.H.,
Surfactant self assembly in cylindrical silica nanopores, J. Phys. Chem. Lett.
1, 1442-1446 (2010).
[4]
Günter, G., Prass, J., Paris, O. and Schoen, M., Novel insights into nanopore
deformation caused by capillary condensation, Phys. Rev. Lett. 101, 086104
(2008).
[5]
Prass, J., Müter, D., Fratzl, P. and Paris, O., Capillarity-driven deformation of
ordered nanoporous silica, Appl. Phys. Lett. 95, 083121 (2009).
[6]
Schoen, M., Paris, O., Günther, G., Müter, D., Prass and Fratzl, P., Lattice
deformations in ordered mesoporous matrices: Experimental studies and
theoretical analysis, Phys. Chem. Chem. Phys. 12 , Advance Article, DOI
10.1039/c000782j (2010).
24
PA-FKP-4: Audi Max, Di, 7 Sept, 14:30 Uhr
Femto-second Spectroscopy:
Measuring the Beat of a Quantum Cascade Laser
W. Parz1, R. Haddad1, T. Müller1, G. Strasser2, and K. Unterrainer1
1
Institut für Photonik, Technische Universität Wien,
Gusshausstraße 25-29, 1040 Wien
2
Institut für Festkörperelektronik, Technische Universität Wien,
Floragasse 7, 1040 Wien
The ultrafast light- matter interaction in quantum cascade lasers below and above
the threshold is explored directly in the time domain with a time resolution of 10 fs.
This is done by generating broadband mid-infrared pulses by phase matched
difference frequency mixing in a 30 μm thick GaSe crystal. The coherent detection
works up to 70 THz, employing the electro optic effect in a ZnTe crystal. This
detection scheme is invariant to the strong co-emitted light fields of the QCL above
threshold, and thus, allows us to measure the whole gain dynamics below and
above the laser threshold [1]. Employing free space coupling to a quantum cascade
laser, we are able to determine the basic static device properties, like gain and
different loss mechanisms in a broad spectral range [2]. Moreover, the high phase
resolution together with time gating methods lets us determine the complex valued
refractive index to a high degree of precision ('n < 7.103) [3]. We also show the
possibility of this method to monitor the instant temperature in the active region
using the thermo- optic effect. Dynamical properties of the gain, like gain relaxation,
were measured in a pump- probe configuration and electro- optic detection.
Generating strong resonant pump pulses in the mid- infrared we find induced
transmission with a population relaxation time of 3 ps, for a laser below threshold.
Above threshold, the relaxation time for induced absorption shortens to below 1 ps.
This life time shortening is a direct consequence of the stimulated emission process
[4].
References
[1] J. Kröll, J. Darmo, S. Dhillon, X. Marcadet, M. Calligaro, C. Sirtori,
K. Unterrainer, Nature 449, 698-701 (2007).
[2] W. Parz, T. Müller, J. Darmo, T. Müller, J. Darmo, M. Austerer, G. Strasser,
L. Wilson, J. Cockburn, A. Krysa, J. Roberts, K. Unterrainer, APL 93, 091105
(2008).
[3] W. Parz, T. Müller, J. Darmo, M. Austerer, G. Strasser, L. Wilson, J.
Cockburn, A. Krysa, J. Roberts, K. Unterrainer, Optics Letters 34, 208 (2009).
[4] W. Kuehn, W. Parz, P. Gaal, T. Müller, J. Darmo, M. Austerer, G. Strasser,
L. Wilson, J. Cockburn, A. Krysa, J. Roberts, K. Unterrainer, APL 93, 151106
(2008).
25
PA-GEP-5: Audi Max, Di, 7 Sept, 14:50 Uhr
Historisch Wertvolle Physikalische Instrumente im Europäischen
Zentrum für Physikgeschichte „Echophysics“ in Schloss Pöllau:
Eine Auswahl aus den Altbeständen der Fakultät für Physik der
Universität Wien
1
2
F. Sachslehner , P. Maria Schuster und B. Strohmaier
3
1
Universität Wien, Fakultät für Physik, Strudlhofgasse 4, 1090 Wien,
[email protected]
2
Victor-Franz-Hess-Gesellschaft, Schloss 1, 8225 Pöllau,Stmk,
[email protected],
3
Universität Wien, Fakultät für Physik, Währingerstr. 17, 1090 Wien,
[email protected]
Einer der Museumsbereiche ist dem „Institut für Radiumforschung der
Kaiserlichen Akademie der Wissenschaften“ in Wien gewidmet, das 1910
eröffnet wurde. Es war weltweit die erste Forschungseinrichtung, die der
Erforschung der physikalischen Eigenschaften des Elements Radium gewidmet
war. Ausgestellt sind Messgeräte der Radioaktivitätsforschung und Möbel,
großteils aus der Originalausstattung dieses „Radiuminstituts“. Die Exponate
sind nunmehr im Besitz der Universität Wien, die sie dem ECHoPhysics
leihweise überlassen hat.
Neben den Leihobjekten, die aus dem ehemaligen Radiuminstitut stammen, gibt
es noch zahlreiche optische und elektrische Objekte, die seit dem Jahr 1902
dem ehemaligen II. Physikalischen Institutes der Universität Wien zuzuordnen
sind. Der Anschaffungszeitraum liegt im Wesentlichen in der zweiten Hälfte des
19. Jahrhunderts und um die Wende vom 19. zum 20. Jahrhundert. Das eine
oder andere Objekt stammt sogar noch aus dem Physikalischen Museum an
der alten Universität Wien und ist über das Physikalische Institut der k. k.
Universität in Wien-Erdberg (Christian Doppler, Andreas von Ettingshausen,
Josef Stefan) in die Türkenstraße 3 im 9. Wiener Bezirk gelangt. Ab 1875 gab
es dort drei Institute: Das Physikalische Institut, das Physikalische Kabinett und
das neue, von Josef Loschmidt geführte Physikalisch-Chemische Institut. Viele
der gezeigten Objekte stammen aus diesem Institut, insbesondere der Periode
von 1891 bis 1902, als Franz S. Exner dessen Vorstand war. Durch die
Neuordnung der physikalischen Institute an der Universität Wien im Jahr 1902
wurde das Physikalisch-Chemische Institut in II. Physikali-sches Institut
umbe-nannt; es übernahm zu dieser Zeit auch Geräte aus dem ursprünglichen
Physikalischen Institut. Hervorzuheben sind die Originalapparate von Josef
Stefan.
26
7. PREISVORTRÄGE / PRIZE LECTURES
Preisvorträge - Prize Lectures
Dienstag – Tuesday, 7 September 2010 / Audi Max
Christian Doppler Preis der Salzburger Landesregierung Christian Doppler Prize of Land Salzburg
11:30 12:30
Rupert Ursin
(IQOQI Wien, ÖAW)
Entangled Photons
Victor Franz Hess Preis des Fachausschusses Kern- und Teilchenphysik Victor Franz Hess Prize
of the Scientific Committee Nuclear and Particle Physics (FAKT)
13:50 14:10
Wolfgang Dungel
(HEPHY, ÖAW)
High precision flavor physics
at the Belle experiment
Wissenschafter des Jahres Scientist of the Year
18:30 20:00
Rudi Grimm
(IQOQI Innsbruck,
ÖAW)
Öffentlicher Vortrag - Public Lecture:
27
Mittwoch - Wednesday 8 September 2010 / Audi Max
Festsitzung Preisverleihung
Prize award celebration session
11:20 – 12:30
Fritz Kohlrausch Prize,
Roman Ulrich Sexl Prize,
Max Auwärter Prize,
Victor Franz Hess Prize,
Anton Paar Prize,
AT&S Prize,
AYPT-IYPT,
Int. Physics Olympiad,
Physik-Fachbereichsarbeiten
Laudationes
Roman Ulrich Sexl Preis/Prize
Gerhard Haas
(Neues Gymnasium
Leoben)
13:15 – 13:45
Brigitte PaganaHammer (GRg3
Wien, Fak. Physik,
Univ. Wien)
Austrian Young Physicists' Tournament
(AYPT)
International Young Physicists' Tournament
(IYPT)
IYPT-Aufgaben: Eine didaktische
Herausforderung für den Physikunterricht
AYPT- IYPT Fight Demonstration, Physics
Olympiad, Physik-Fachbereichsarbeiten
13:45 – 14:15
Fritz Kohlrausch Preis/Prize
14:15 – 14:55
Francesca Ferlaino
(Univ. Innsbruck)
Few-Body Physics with Ultracold Gases:
The Fascinating Case of Cesium
14:35 – 14:55
Thomas Müller
(TU Wien)
Carbon-Based Optoelectronics
Max Auwärter Preis/Prize
14:55 – 15:35
Stephen Berkebile
(Univ. Graz)
Epitaxial Organic Films and Their Interfaces:
Growth and Electronic Structure
28
Donnerstag - Thursday 9 September 2010 / Grüner Hörsaal
AT&S Preis des Fachausschusses Festkörperphysik AT&S Prize of the Scientific Committee Solid State Physics (FKP)
16:35 - 16:50
Florian Libisch
(TU Wien)
Simulation of coherent, large-scale
nanostructures
Anton Paar Preis des Fachausschusses Festkörperphysik Anton Paar Prize of the Scientific Committee Solid State Physics (FKP)
17:05 - 17:20
Daniel Primetzhofer
(Univ. Linz)
Electronic interactions of slow ions
Î Abstracts Ursin, Grimm see Plenary Talks and Public Lectures p. 17
Î Victor Franz Hess Prize Lecture: Abstract see Physics in Austria p. 23
Î AT&S Prize Lecture: Abstract see Topical Session FKP-NESY p. 104
Î Anton Paar Prize Lecture: Abstract see Topical Session FKP-NESY p. 107
PV-1a: Audi Max, Mi, 8 Sept, 13:15 Uhr
Roman Ulrich Sexl Preisvortrag
Das AYPT
Gerhard Haas
Neues Gymnasium Leoben
Das AYPT ( Austrian Young Physicists Tournament ), veranstaltet vom Verein
AYPT – Forschungsforum junger Physiker, welches alljährlich in Leoben stattfindet,
dient dazu jene Schüler auszuwählen, die als Nationalteam Österreich beim
entsprechenden internationalen Turnier ( IYPT), der sog. Physik- WM, vertreten
sollen. Im vorliegenden Beitrag wird auf die Entwicklung des AYPT in Österreich,
den Ablauf des Turniers sowie auf die Ziele dieser Veranstaltung eingegangen.
29
PV-1b: Audi Max, Mi, 8 Sept, 13:30 Uhr
Roman Ulrich Sexl Preisvortrag
IYPT-Aufgaben: Eine didaktische Herausforderung für den
Physikunterricht
B. Pagana-Hammer
Landstraßer Gymnasium, SSR Wien, Fakultät für Physik, Univ. Wien
Die Aufgabenstellungen, die zur Vorbereitung auf die Teilnahme am International
Young Physicists‘ Tournament (IYPT) bearbeitet werden müssen, sind das
Kernstück dieses Wettbewerbs. Die im Laufe des Jahres zu bearbeitenden 17
kleinen Forschungsprojekte geben den Teilnehmerinnen und Teilnehmern
Gelegenheit forschend zu lernen und zu einem selbstständig erworbenen
Erkenntnisgewinn zu gelangen. Die selbständige Aneignung von Wissen durch die
Beschäftigung mit den IYPT- Aufgaben, den sogenannten Tasks, lässt sich auch im
Regelunterricht nützen und eröffnet völlig neue fachdidaktische Perspektiven. Die
Schülerinnen und Schüler gewinnen Einblick in das Wesen der
Naturwissenschaften, des naturwissenschaftlichen Arbeitens und der Forschung.
Dadurch wird ein Konzeptwechsel in der Einstellung zu den Naturwissenschaften
vollzogen, und ein innovativer Zugang zur naturwissenschaftlichen Bildung
ermöglicht. Die persönliche Erfahrung im wissenschaftlichen Arbeiten wirkt sowohl
der unkritischen Akzeptanz als auch der unreflektierten Ablehnung der
Naturwissenschaften, insbesondere der Physik, entgegen. Wie eigenständige
Erkenntnisprozesse mit Hilfe von IYPT-Aufgaben im Physikunterricht initiiert und
begleitet werden können, soll im vorliegenden Beitrag an Hand eines konkreten
Beispiels skizziert werden.
PV-1c: Audi Max, Mi, 8 Sept, 13:45 Uhr
IYPT 2010
Austrian Team, 2nd place among 23 teams: Michael Scherbela, Johannes
Tiefnig, Bernhard Zatloukal (Bischöfliches Gymnasium Graz), Martin Schnedlitz
(Seebacher Gymnasium Graz), Philipp Heise (BRG Auhof-Linz)
Team Leader: Dieter Winkler (Bischöfliches Gymnasium Graz), Angel Usunov
(IYPT - Forschungsforum junger Physiker)
PV-1d: Audi Max, Mi, 8 Sept, 13:55 Uhr
International Physics Olympiad 2010
Silver Medalists: Michael Scherbela (Bischöfliches Gymnasium Graz), Andeas
Theiler (HTL Weiz); Bronze Medalist: Stephan Troyer (BG/BRG Mödling
Keimgasse): Honorable Mention: Philipp Heise (BRG Auhof-Linz)
Advisors: Helmut Mayr (BGRG Wien-15/Schmelz, Sir Karl Popperschule/Wien-4),
Engelbert Stütz (BRG Auhof-Linz)
30
PV-1e: Audi Max, Mi, 8 Sept, 14:05 Uhr
Physik-Fachbereichsarbeiten
Prämierte Schüler: Markus Kunesch (Akad. Gym. Wien), Andreas Hakon
Kretschmer (GRG Rosasgasse), Sebastian Schnaubelt (BG/BRG Horn)
Betreuer: Katrin Graf (Akad. Gym. Wien), Andrea Mayer (GRG Rosasgasse), Hans
Hofbauer (BG/BRG Horn).
PV-2a: Audi Max, Mi, 8 Sept, 14:15 Uhr
Fritz Kohlrausch Prize Lecture
Few-Body Physics with Ultracold Gases:
The Fascinating Case of Cesium
F. Ferlaino1, M. Berninger2, A. Zenesini2, B. Huang2, H.-C. Nägerl2 and R. Grimm2,3
1
Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria,
[email protected]
2
Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria,
3
Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der
Wissenschaften, 6020 Innsbruck, Austria
In 1970, Vitaly Efimov predicted one of the most counterintuitive phenomena in fewbody physics. He found that a system of three strongly interacting particles supports
an infinite series of “giant” three-body bound states, known as trimer states, with a
Russian-doll-type scaling. Despite the great attention the Efimov effects has
attracted in various fields, ranging from nuclear to molecular physics, its observation
remained an elusive goal for 35 years.
With the advent of ultracold atomic and molecular systems with tunable interaction
novel possibilities of investigation opened up. Cesium is the first species that has
revealed signatures of Efimov states and related few-body phenomena. I will first
give an overview of our previous observations on three-body recombination [1] and
atom-dimer relaxation [2]. I will then present our results on four-body systems [3]
and discuss how all these observations fit together in the Efimov scenario. Finally, I
will report on the progress of our current experiments, which are dedicated to a
comparison of Efimov features on different Feshbach resonances and to the search
of tetramer states in dimer-dimer collisions.
References
[1]
T. Kraemer, M. Mark, P. Waldburger, J. G. Danzl, C. Chin, B. Engeser, A. D.
Lange, K. Pilch, A. Jaakkola, H. -C. Nägerl, and R. Grimm, Nature 440, 315
(2006).
[2]
S. Knoop, F. Ferlaino, M. Mark, M. Berninger, H. Schöbel, H. -C. Nägerl, and
R. Grimm, Nature Phys. 5, 227 (2009).
[3]
F. Ferlaino, S. Knoop, M. Berninger, W. Harm, J. P. D'Incao, H. -C. Nägerl,
and R. Grimm, Phys. Rev. Lett. 102, 140401 (2009).
31
PV-2b: Audi Max, Mi, 8 Sept, 14:35 Uhr
Fritz Kohlrausch Prize Lecture
Carbon-Based Optoelectronics
T. Müller
Technische Universität Wien, Institut für Photonik, Gußhausstraße 27-29
A 1040 Wien
Carbon-based materials exhibit extraordinary physical properties and have
therefore attracted much attention from both universities and the electronics
industry. In this talk I will review our research activities on the optical and
optoelectronic properties of graphene and carbon nanotubes. Specifically, I will
present photoconductivity studies of graphene [1], I will discuss the origin of its
photoconductive behaviour [2], and present an ultrafast (>40 GHz) metal-graphenemetal photodetector [3]. We used this graphene-based photodetector to
demonstrate the faithful detection of data streams at rates of 10 gigabits per second
[4]. In our carbon nanotube work, we fabricated split-gate, single nanotube diodes.
We then utilized the radiative electron-hole recombination of the carriers generated
at the p-n junction to produce the first nanotube true light-emitting diode [5]. The
efficiency of this diode was orders of magnitude higher than what had been
achieved previously using ambipolar nanotube transistors, had much lower power
consumption and a significantly narrower linewidth. This light emitting diode opens
up the possibility of developing nanotube single-photon sources and other
nanodevices.
References
[1]
F. Xia, T. Mueller, R. Golizadeh-Mojarad, M. Freitag, Y. Lin, J. Tsang,
V. Perebeinos, and Ph. Avouris, “Photocurrent imaging and efficient photon
detection in a graphene transistor”, Nano Lett. 9, 1039 (2009)
[2]
T. Mueller, F. Xia, M. Freitag, J. Tsang, and Ph. Avouris, “Role of contacts in
graphene transistors: A scanning photocurrent study”, Phys. Rev. B 79,
245430 (2009)
[3]
F. Xia, T. Mueller, Y. Lin, A. Valdes-Garcia, and Ph. Avouris, “Ultrafast
graphene photodetector”, Nature Nanotechnol. 4, 839 (2009)
[4]
T. Mueller, F. Xia, and Ph. Avouris, “Graphene photodetectors for highspeed optical communications”, Nature Photon. 4, 297 (2010)
[5]
T. Mueller, M. Kinoshita, M. Steiner, V. Perebeinos, A. A. Bol, D. B. Farmer,
and Ph. Avouris, “Efficient narrow-band light emission from a single carbon
nanotube p-n diode”, Nature Nanotechnol. 5, 27 (2009)
32
PV-3: Audi Max, Mi, 8 Sept, 14:55 Uhr
Max Auwärter Prize Lecture
Epitaxial Organic Films and Their Interfaces:
Growth and Electronic Structure
S. Berkebile
Institute of Physics, Karl-Franzens University Graz, Austria
An understanding of the interfaces in molecular organic thin films is crucial to the
improvement of organic electronic devices. The interactions at interfaces between
different organic layers and inorganic contact and support materials are major
determinants of important factors in organic thin films such as electronic level
alignment between different materials, molecular orientation and geometric
structure within the organic layers, and the process of crystalline film growth.
A study of three rod-like organic molecules on three inorganic substrates has been
conducted using a variety of measurement techniques to gain a systematic insight
into these issues. Particular attention has been given to the orientation and ordering
in the first few molecular layers and the consequences of the structure of these first
layers upon further crystalline growth in thin films.
It will be shown that with the appropriate choice of substrate and growth conditions,
well-ordered and oriented monolayer and ‘single’ crystalline films of conjugated
organic molecules can be grown for further controlled studies. Such films are a
prerequisite for experimental band structure determination in defined
crystallographic directions and the measurement of the momentum-distribution of
individual molecular orbitals with angle-resolved ultraviolet photoemission
spectroscopy (ARUPS). Measurements of the inter- and intramolecular dispersion
in organic molecular crystals has led to the reconstruction of real-space molecular
orbitals from photoemission data and can be used to study both basic and practical
properties of organic molecular thin films and monolayers, such as interactions at
organic/inorganic interfaces including pi-orbital – metal hybridization and the basic
electronic structure in systems of limited size and low dimensions.
This work was supported by the Austrian Science Foundation FWF. We
acknowledge the Helmholtz-Zentrum Berlin – Electron storage ring BESSY II for
provision of synchrotron radiation at beamline TGM-4. The research leading to
these results has received funding from the European Community's Seventh
Framework Programme (FP7/2007-2013) under grant agreement n.°226716.
33
8. FACHTAGUNGEN / TOPICAL SESSIONS
8.1 ACP – Arbeitskreis Chancengleichheit Physik
Donnerstag - Thursday 9 September 2010 / HS 411
Arbeitskreis Chancengleichheit Physik Working Group Equal Opportunities in Physics (ACP)
Parallel Session ACP
Zeit-Time
9:00 - 11:00
Vorsitzende
Chairwoman
Thema - Topic
Regina Hitzenberger
(Univ. Wien)
Offene Diskussion von Themen des
Arbeitskreises - Erstellung einer Agenda
für die nächsten Jahre;
Open discussion on topics
of the working group set-up of an agenda for the next years
34
8.2 AKU – Akustik
Fachausschuß Akustik - Scientific Committee Acoustics (AKU)
Parallel Session AKU
Zeit-Time
Vortragender
Lecturer
Vortragstitel
Title of Lecture
13:30 - 13:50
Holger Waubke (ÖAW)
Randelemente Methode mit numerisch
bestimmter Greenscher Funktion
13:50 - 14:10 Wolfgang Kreuzer (ÖAW)
Verwendung der Randelemente
Methode zur Berechnung von BaffleProblemen in der Akustik
Georg Rieckh (ÖAW)
Simulation der Wirkung verschiedener
Schallschutzwandtypen
Ferhat Kiymaz (ÖAW)
Hörprobenauswahl zur Diagnose der
auditiven Wahrnehmung anhand
mathematischen und statistischen
Werkzeugen
14:50 - 15:10
Michael Mihocic (ÖAW)
EXPSUITE: Software Framework zur
Durchführung psychoakustischer
Experimente
15:10 - 15:30
Ewald Enzinger (ÖAW)
Einfluss des GSM/UMTS Adaptive
Multirate (AMR) Sprachcodecs
auf Formantmessungen
14:10 - 14:30
14:30 - 14:50
35
AKU-1: HS 412, Do, 9 Sept, 13:30 Uhr
Randelemente Methode mit numerisch bestimmter
Greenscher Funktion
H. Waubke1, G. Rieckh1 and W. Kreuzer1
1
Institut für Schallforschung, Österreichische Akademie der Wissenschaften,
Wohllebengasse 12-14, A-1040 Wien, [email protected]
Eine analytische Lösung für Wellen einen horizontal geschichteten Halbraum lässt
sich im Fourier-transformierten Raum angeben. Die Fourier-Rücktransformation
über die horizontalen Richtungen hat numerisch zu erfolgen. Um auch Tunnel und
Einschnitte behandeln zu können, soll mittels der Fourier-Transformation die
Greensche Funktion ermittelt werden. Diese Funktion ist das Fundament der
Randelemente Methode. Liegen Auswertepunkt und Punkt der Test-Belastung
aufeinander, so wird die Funktion singulär und ist mithin schlecht numerisch zu
behandeln. Dieses Problem kann jedoch umgangen werden, wenn die Integration
über das Randelement vor der Fourier-Rücktransformation ausgeführt wird. In
diesem Fall verbleibt ein einfaches Integral über eine reguläre Funktion übrig, die
gegenüber der sonst notwendigen Fourier-Rücktransformation noch mittels einer
sinc Funktion abgeschwächt wird, wenn man gegen unendlich geht. Mit diesem
Ansatz ist es möglich, die direkte Randelemente Methode in Verbindung mit der
numerisch bestimmten Greenschen Funktion zu verwenden.
Darüber hinaus kann man die Randelemente Methode im einfach transformierten
Raum ansetzen, sofern der Tunnel oder Einschnitt gerade ist. Anstelle eines
dreidimensionalen Problems wird eine Folge von unabhängigen zweidimensionalen
Querschnittsmodellen für jede Wellenzahl generiert. Dieses Vorgehen wird in der
Literatur auch als 2.5D Verfahren bezeichnet [1].
Literatur
[1] Tang, Z., Liu, Q. H., “The 2.5D FDTD and Fourier PSTD methods and
applications”, Microwave and Optical Technology Letters 36 (6), 430-436 (2003)
AKU-2: HS 412, Do, 9 Sept, 13:50 Uhr
Verwendung der Randelemente Methode zur Berechnung
von Baffle-Problemen in der Akustik
Z.-S. Chen1 , W. Kreuzer1, H. Waubke1 und A. J. Svobodnik2
1
Österreichische Akademie der Wissenschaften, Institut für Schallforschung,
Wohllebengasse 12-14, A-1040 Wien; E-Mail: [email protected]
2
Harman International, Wien
36
Um zum Beispiel das Abstrahlverhaltens eines Hochfrequenzlautsprechers
(Tweeter) zu simulieren, ist es möglich, den Lautsprecherkasten, der im Vergleich
zum Tweeter sehr groß ist, als schallhart reflektierende Platte (Baffle), in der der
Tweeter eingebaut ist, zu modellieren. Die Schallabstrahlung kann dann mit Hilfe
der Randelemente Methode (BEM) numerische berechnet werden.
Um die Berechnungen effizient durchführen zu können, wird der Raum in drei SubRäume zerlegt. Einen Halbraum :2 vor dem Baffle, einen Halbraum :3 dahinter
und einen geschlossenen Raum :1 um das abstrahlende Objekt herum. Durch die
Verwendung der Halbräume muss der Baffle nur in :1 diskretisiert werden,
außerhalb wird er durch eine Randbedingung im Halbraums definiert.
Es ist bekannt, dass die numerische Lösung eines akustischen Aussenraumproblems für gewisse kritische Frequenzen eine nicht eindeutig ist. Um dennoch
eine eindeutige Lösung zu garantieren, wird die Randelemente Methode mit einer
Burton Miller Formulierung verwendet.
AKU-3: HS 412, Do, 9 Sept, 14:10 Uhr
Simulation der Wirkung verschiedener Schallschutzwandtypen
G. Rieckh1, H. Waubke1, W. Kreuzer1 and Z. Chen1
1
Institut für Schallforschung, Österreichische Akademie der Wissenschaften,
Wohllebengasse 12-14, A-1040 Wien, [email protected]
Mit zunehmendem Verkehr und strengeren Schallschutzbestimmungen ist es
zunehmend wichtig die akustische Wirkung von Schallschutzwänden nicht nur
durch eine Steigerung von deren Höhen zu verbessern, sondern auch verschiedene
Formen und absorbierende Materialien zu studieren. Zu diesem Zweck wurde eine
Studie durchgeführt, bei der verschieden Typen von Schallschutzwänden in einer
Simulation miteinander verglichen wurden. Die Simulation beruht auf einer
zweidimensionalen Formulierung der Randelementemethode [1]. Sie berücksichtigt
sowohl Form und Absorptionsvermögen der Schallschutzwand, als auch Effekte,
die auf die das umliegende Gasland zurückzuführen sind. Von speziellem Interesse
ist die für die Randelementemethode nötige Green’sche Funktion für den Halbraum
mit Impedanzrandbedingungen.
Literatur
[1] Waubke, H., Chen, Z., Kreuzer, W., “Auralization of noise recordings behind a
simulated noise barrier”, Fortschritte in der Akustik, Proceedings of the
NAG/DAGA09, Rotterdam, p.637-640 (2009).
37
AKU-4: HS 412, Do, 9 Sept, 14:30 Uhr
Hörprobenauswahl zur Diagnose der auditiven Wahrnehmung anhand
mathematischen und statistischen Werkzeugen
F. Kiymaz
Institut für Schallforschung der Österreichischen Akademie der Wissenschaften,
Wohllebengasse 12-14, 1040 Wien, Österreich, E-mail: [email protected]
Um eine Aussage über „Lästigkeit“ von Lärm machen zu können, muss man die
psychoakustischen Faktoren von Lärm mit in die Aussage einbeziehen. Um die
Wirksamkeit von Schallreduzierungsmaßnahmen fest zu stellen, wurde das Institut
für Schallforschung im Rahmen eines Projektes mit Erstellung und Durchführung
von akustischen Wahrnehmungstests beauftragt. In einer Vorsynthese wurden aus
den an uns gelieferten Messdaten, Signale der Schallereignisse rekonstruiert, und
deren Schallattribute mit dem hausinternen Softwaretool S_Tools-STx errechnet.
Aus den bearbeiteten Ausgangsdaten, (über 10.000 voneinander unterschiedliche
Schallereignisse) wurden einige wenige, aussagekräftige ausgewählt. Sie werden in
Form von psycho-akustischen Wahrnehmungstest an Testpersonen ausgewertet.
Eine große Anzahl an Ausgangsdaten erforderte die Auswahl der Testsequenzen
unter Verwendung von mathematischen und statistischen Werkzeugen, wie
Gruppierungsverfahren, Mittelwertbildung und Approximationsverfahren an
Schallattributen, die nach einer der Vorgängerprojekte [1] des Instituts für
Schallforschung, für das Störempfinden des menschlichen Gehörs als relevant
gekennzeichnet waren. Für die ausgewählten Testsequenzen werden an 20 normal
hörenden Testpersonen unterschiedlicher Altersgruppen psychoakustische
Wahrnehmungstests durchgeführt. Anhand der Auswertung der Tests werden wir
ggf. eine Änderung in Störempfinden des Menschen bei variierenden
Schallreduzierungsmaßnahmen feststellen. Dadurch können wir die Grundfrage
„Welche Schallschutzmaßnahmen wirken bei den gegebenen Randbedingungen
besser als andere“ beantworten.
References
[1] Deutsch, Werner A., “Automatische Lärmbewertung von Zugsvorbeifahrten”,
DAGA 2007.
38
AKU-5: HS 412, Do, 9 Sept, 14:50 Uhr
Expsuite: Software Framework zur Durchführung
psychoakustischer Experimente
M. Mihocic, P. Majdak und B. Laback
Institut für Schallforschung Wien, Österreichische Akademie der Wissenschaften,
[email protected]
Am Institut für Schallforschung werden seit 2003 psychoakustische Experimente mit
akustischer und elektrischer Stimulation (Cochleaimplantate) durchgeführt. Vier
Testplätze dienen der Durchführung psychoakustischer Studien und akustischer
Messungen: Zwei doppelwandige Schallkammern der Type IAC-1202A, die für
psychoakustische Tests mit Kopfhörern sowie Sprach- und Audioaufnahmen
verwendet werden. Die Bedienung erfolgt mit je einem Computer, wobei 2-KanalAudio mit Abtastraten von 192 kHz zur Verfügung steht. Ein reflexionsarmer Raum
in der Größe 6 x 6 x 3 m steht für akustische Tests im Quasi-Freifeld zur Verfügung.
Der Raum unterstützt 24 bidirektionale, mit einem Computer verbundene, AudioKanäle sowie Audio- und Videoüberwachung und wird für Projekte wie Messung
der
Außenohrübertragungsfunktionen,
Schallquellenlokalisationstests
und
akustische Holografie verwendet. Ein räumlich abgegrenzter Testplatz für
Experimente mit Cochleaimplantat-Trägern bietet die Möglichkeit der direkten
bilateralen elektrischen Stimulation mittels computergenerierter Signale.
Für die Ansteuerung der Hardware wird ExpSuite als Software-Lösung verwendet.
ExpSuite besteht aus einem Framework und den darauf basierenden Applikationen.
Dabei profitiert sie von der „Rapid Application Development”-Umgebung in Visual
Basic, die eine schnelle Entwicklung der Experimente ermöglicht. Durch den
modularen Aufbau kann der Applikationsprogrammierer das Verhalten der
Applikationen selbst definieren: zum Beispiel die Generierung einer Tabelle mit
Testparametern und Ergebnissen (Item list), die Erzeugung und das Abspielen der
Stimuli, den Ablauf des Experiments oder die Auswertung der Ergebnisse. Das
Framework selbst unterstützt prozedurelle Eigenschaften wie zeitliche Struktur (z.B.
adaptive und ineinander verschachtelte Abläufe), Parametrierung der einzelnen
experimentellen Schritte, technische Anforderungen wie Steuerung über Joypad,
Maus und Tastatur oder Verwendung von Touchscreen, Drehteller und PositionsTracking-Systemen. Damit kann sich der Applikationsprogrammierer auf die
Entwicklung des experimentellen Designs konzentrieren. Die auf der Item list
basierende Oberfläche hat sich seit Jahren bewährt und wird ständig weiter
entwickelt. Mit der direkten Anbindung an Matlab steht den ExpSuite-Applikationen
eine Vielfalt von Matlab-internen Funktionen zur Verfügung, die auch zur direkten
Auswertung der Ergebnisse verwendet werden können.
Die Ausgabe der in vektororientierter Form in Matlab erzeugten Stimuli kann über
herkömmliche akustische Audiogeräte oder als elektrische Stimulation über ein
Cochleaimplantat-Interface erfolgen. Das Programm Pure Data (pd) übernimmt die
akustische Signalverarbeitung in Echtzeit (z.B. komplexe Filterung und
Signalgenerierung), die Ausgabe der Stimulationsdateien, sowie die simultane
Aufnahme und Wiedergabe mehrerer Audiokanäle. Die elektrische Stimulation zur
39
Durchführung von Experimenten mit Cochleaimplantat-Trägern erfolgt über die
Research Interface Boxen (RIBs), die eine binaural synchronisierte Stimulation der
Med-El Prozessoren unterstützen.
ExpSuite wird am Institut für Schallforschung entwickelt und gepflegt. Sie ist unter
der European Union Public License (EUPL) lizenziert und steht unter
http://expsuite.sourceforge.net allen interessierten zur Verfügung.
AKU-6: HS 412, Do, 9 Sept, 15:10 Uhr
Einfluss des GSM/UMTS Adaptive Multirate (AMR)
Sprachcodecs auf Formantmessungen
E. Enzinger
Institut für Schallforschung, Österr. Akademie der Wissenschaften,
[email protected]
Der bei GSM und UMTS zur Sprachübertragung verwendete Adaptive Multirate
(AMR) Codec sieht acht Qualitätsstufen mit unterschiedlichen Bitraten vor.
Während eines Gesprächs wird auf Basis der Kanalübertragungsqualität die
optimale Stufe ausgewählt. Um Unterschiede bei durch auf LPC basierenden
automatischen Trackern ermittelten Formantspuren zu untersuchen, wurden
Studioaufnahmen mit den verschiedenen Codecstufen en- und dekodiert und
anschließend Formantfrequenzen in Vokalen extrahiert. Dies hat besondere
Relevanz für forensische Sprechervergleiche auf Basis von Formanten, wenn die
Vergleichsaufnahmen von Gesprächen über Mobiltelefone stammen.
40
8.3 AMP – Atome, Moleküle, Quantenphysik und Plasmen /
Fachausschuss Atome, Moleküle, Quantenphysik, und Plasmen
Scientific Committee Atoms, Molecules, Quantum Optics,
and Plasmas (AMP)
Parallel Session AMP
Zeit-Time
Vortragender Lecturer
Vortragstitel - Talk Title
09:00 - 09:30
Gregor Weihs
(Univ. Innsbruck)
Three slits rule out multi-order interference
09:30 - 09:45
Marcus Huber
(Univ. Wien)
Detection and classification of genuine
multipartite entanglement in highdimensional mixed states
09:45 - 10:00
Christoph Uiberacker
(MU Leoben)
Resonant population transfer in N-level
systems by arbitrary pulses
10:00 - 10:30
Beatrix Hiesmayr
(Univ. Wien)
Testing foundations of quantum
mechanics in particle physics
11:00 11:30
Pause - Coffee Break
41
Fachausschuss Atome, Moleküle, Quantenphysik, und Plasmen
Scientific Committee Atoms, Molecules, Quantum Optics, and
Plasmas (AMP)
Parallel Session AMP
Zeit-Time
13:30 - 14:00
Martin Ratschek
(TU Graz)
Electron spin resonance in doped helium
nanodroplets as tool to study magnetic
properties and spin dynamics
14:00 - 14:15
M. Ellmeier
(TU Graz)
Contrast measurements of CPT resonances
87
formed on the Rb D1 and D2 line
14:15 - 14:30
T. Gruber
(TU Graz)
Ab initio spin densities of small
alkali-metal doped helium droplets
14:30 - 14:45
Peter Cristofolini
(Univ. Innsbruck)
Towards the generation of entangled
photon pairs in microcavities
14:45 - 15:00
Florian Lackner
(TU Graz)
Photoionization of Rb atoms on
He nanodroplets
15:00 - 15:15
Elisabeth Schwarz
(TU Wien)
Plasma generation by combination
of two laser wavelengths
15:15 - 15:30
Christoph Spengler
(Univ. Wien)
A composite parameterization of unitary
groups, density matrices and subspaces
42
AMP-1 HS 414, Do, 9 Sept. 2010, 09:00 Uhr
Three Slits Rule Out Multi-Order Interference
G. Weihs1,2, U. Sinha2, I. Söllner1, C. Couteau3, T. Jennewein2 and R. Laflamme2,4
1
Institut für Experimentalphysik, Universität Innsbruck,
Technikerstraße 25, 6020 Innsbruck, Austria, [email protected]
2
Institute for Quantum Computing and Dept. of Physics and Astronomy, University
of Waterloo, 200 University Avenue West, Waterloo ON N2L3G1, Canada
3
Laboratoire de Nanotechnologie et d’Instrumentation Optique, Université de
Technologie de Troyes, 12 rue Marie Curie, 10 000 Troyes, France
4
Perimeter Institute for Theoretical Physics,
31 Caroline Street North, Waterloo N2L2Y5, Canada
In Ref. [1] Sorkin investigated the possibility that quantum mechanics might be
formulated as a generalized measure theory. Born's rule that quantum mechanical
probabilities are absolute squares of complex amplitudes results in the interference
of possible evolutions, just like in the interference of classical waves. Quantum
mechanical interference violates the sum rule that probabilities of mutually exclusive
events can be added. One can imagine a yet more general theory by assuming that
it violates the next higher sum rule about the additivity of probabilities of three
mutually exclusive possibilities. Standard quantum mechanics does obey this
second sum rule and so does any classical wave theory. In other words,
interference only occurs from all possible pairwise combinations of possibilities.
A violation of that second sum rule would mean that there is higher order
interference and that Born’s rule would have to be modified. This would have
dramatic implications, most likely resulting in a nonlinear theory. It has further been
shown that a modification of Born’s rule would allow computation that is more
powerful than quantum computation, as well as perfect distinction of non-orthogonal
quantum states. The latter would render quantum key distribution as we know it
impossible.
We experimentally tested the validity of the second sum rule by measuring the
interference patterns produced by three slits and all the possible combinations of
these slits being open or closed [2]. We use either attenuated laser light or a
heralded single photon source combined with single photon counting to confirm the
particle character of the measured light. Within our experimental accuracy and
Born's rule is vindicated and the second sum rule appears to be obeyed [3].
References
[1]
R. D. Sorkin, Quantum Mechanics as Quantum Measure Theory, Mod. Phys.
Lett. A 9, 3119 (1994).
[2]
U. Sinha, C. Couteau, Z. Medendorp, I. Söllner, R. Laflamme, R. Sorkin, and
G. Weihs,
Testing Born's Rule in Quantum Mechanics with a Triple Slit Experiment in
Foundations of Probability and Physics - 5, Accardi, L.; Adenier, G.; Fuchs,
C.; Jaeger, G.; Khrennikov, A.; Larsson, J. & Stenholm, S. (ed.), AIP
Conference Proceedings 1101, 200-207 (2009).
43
AMP-2 HS 414, Do, 9 Sept. 2010, 09:30 Uhr
Detection and Classification of Genuine Multipartite Entanglement
in High-Dimensional Mixed States
M. Huber1, Andreas Gabriel2 and Beatrix Hiesmayr3
1
University of Vienna, Boltzmanngasse 5, A1090 Vienna,
[email protected]
2
University of Vienna, Boltzmanngasse 5, A1090 Vienna
3
We present a general framework to identify genuinely multipartite entangled mixed
quantum states in arbitrary-dimensional systems and show on exemplary cases that
the constructed criteria are stronger than previously known ones. Our criteria are
simple inequalities involving matrix elements of the given quantum state and detect
genuine multi-partite entanglement that had not been identified so far. They are
experimentally accessible without quantum state tomography and are easily
computable as no optimization or eigenvalue evaluation is needed. We also provide
an optimal way for constructing the observables needed to identify the separability.
Also we show that with such inequalities it is possible to distinguish certain classes
of genuinely multipartite entangled states, e.g. the GHZ and W class. Furthermore
these criteria prove to be versatile tools for detecting separability with respect to
different partitions of multipartite states and provide novel ways of deriving lower
bounds on concurrence based entanglement measures. In the end we show how
with the help of such a framework, one can go further and not only identify genuine
multipartite entanglement, which is constituted by non-2-separability, but generalize
it to achieve criteria for non-k-separability in arbitrary dimensional multipartite
states.
References
[1]
M. Huber, F.Mintert, A. Gabriel and B.C. Hiesmayr, „Detection of HighDimensional Genuine Multipartite Entanglement of Mixed States“, Phys.
Rev. Lett. 104, 210501 (2010)
[2]
A. Gabriel, B.C. Hiesmayr and M, Huber, „Criterion for k-separability in
mixed multipartite systems“, arXiv/quant-ph: 1002.2953
44
AMP-3 HS 414, Do, 9 Sept. 2010, 09:45 Uhr
Resonant Population Transfer in N-Level Systems by Arbitrary Pulses
C. Uiberacker1 and W. Jakubetz2
1
Montanuniversität Leoben, Inst. f. Physik; [email protected]
Universität Wien, Inst. f. theoretische Chemie
2
N-level models are used in a variety of fields like biological and chemical systems
(e.g. isomerization reactions [1]) but also quantum computing, quantum optics or
spintronics. Furthermore in recent years strong short laser pulses became available
[2]. Various control strategies [3,4] have been explored in order to steer population
to a chosen level in reactions. The resulting pulse fields are usually complicated
and hard to interpret, which favours an analytic approach providing simple rules [5].
By assuming the experimental pulse to have finite support in time and interpreting
the duration as one period of a periodic signal we use Floquet theory to analyse the
propagator. We find that the criterion on the Floquet eigenvalues for full population
transfer given by Holthaus [6] for adiabatic pulses can be generalized to arbitrary
pulses. However it turns out that this criterion is only necessary and the
eigenvectors are needed to provide a sufficient criterion.
References
[1]
C.Uiberacker and W.Jakubetz, “Molecular isomerization induced by
ultrashort infrared pulses. I. Few-cycle to sub-one-cycle gaussian pulses and
the role of the carrier-envelope phase“, J.Chem.Phys. 120,11532 (2004),
ibid., “Molecular isomerization induced by ultrashort infrared pulses. II.
Pump-dump isomerization using pairs of time-delayed half-cycle pulses“,
J.Chem.Phys. 120, 11540 (2004)
[2]
T. Brabec and F. Krausz, “Intense few-cycle laser fields: Frontiers of
nonlinear optics”, Rev. Mod. Phys. 72, 545 (2000)
[3]
H. Rabitz, R. de Vivie-Riedle, M. Motzkus, K. Kompa, “Whither the Future of
Controlling Quantum Phenomena?”, Science 288, 824 (2000)
[4]
M. Seidl, M. Etinski, C. Uiberacker and W. Jakubetz, “Pulse-train control of
branching processes: Elimination of background and intruder state
population”, J. Chem. Phys. 129, 234305 (2008)
[5]
C.Uiberacker and W. Jakubetz, “Strong-field dipole resonance: Limiting
analytical cases”, Phys. Rev. A 80, 063406 (2009)
[6]
M. Holthaus, “Pulse-Shape-Controlled Tunneling in a Laser Field”, Phys.
Rev. Lett. 69, 1596 (1992)
45
AMP-4 HS 414, Do, 9 Sept. 2010, 10:00 Uhr
Testing foundations of Quantum Mechanics in Particle Physics
T. Adaktylos1, A. Gabriel1, B.C. Hiesmayr12, F. Hipp1, M. Huber1, G. Krizek1,
S. Radic1, H. Schimpf1, Ch. Spengler1 and H. Waldner1
1
University of Vienna, Faculty of Physics, Botzmanngasse 5, A-1090 Vienna
University of Sofia, Faculty of Physics, Blvd. James Bourchier 5, 1164 Sofia,
Bulgaria
2
Particle physics has become an interesting testing ground for questions of
foundations of quantum mechanics. Entangled massive meson-antimeson systems
are specially suitable as they offer a unique laboratory to test various aspects of
particle physics (CP violation, CPT violation,...) as well to test foundations of
quantum mechanics, e.g. Bell inequalities [1, 2, 3, 4], decoherence effects [5, 6],
quantum marking and erasure concepts [7, 8], Bohr's complementary relation
[9, 10]. The main aim of this talk is to show that these systems not consisting of
ordinary matter and light provide novel insights into quantum theory. Particularly, we
show that a certain Bell inequality is related to the observed tiny difference between
matter and antimatter [3, 4], the so called CP violation explored in particle physics.
Herewith two different powerful concepts in physics, entanglement or its
manifestation and symmetry, become related. Then we show a Bell inequality
sensitive to the quantum number strangeness [3], which is not violated for the
maximally entangled spin singlet state, but surprisingly for a non-maximally
entangled state [1]. This opens for the first time the possibility of a direct
experimental. We will shortly discuss the status quo of the realization [11] with the
upgraded KLOE detector (DAPHNE machine, Italy). In summary, understanding the
nature of entanglement and its manifestation needs also studies of entanglement at
different energy scales and as recent works show there are still many open
questions concerning entanglement, e.g. about high dimensional genuine
multipartite entanglement [12] or of relativistic entanglement of massive spin 1/2
particles [13].
References
[1]
B.C. Hiesmayr: Nonlocality and entanglement in a strange system.European
Physical Journal C, Vol. 5073-79 (2007).
[2]
B.C. Hiesmayr: A generalized Bell inequality and decoherence for the K0
anti-K0 system. Found. of Phys. Lett. 14, 231 (2001).
[3]
R.A. Bertlmann and B.C. Hiesmayr: Bell inequalities for entangled kaons
and their unitary time evolution. Phys. Rev. A 63, 062112 (2001).
[4]
R.A. Bertlmann, W. Grimus and B.C. Hiesmayr: Bell inequality and CP
violation in the neutral kaon system. Phys. Lett. A 289, 21 (2001).
[5]
R.A. Bertlmann, K. Durstberger and B.C. Hiesmayr: Decoherence of
entangled kaons and its connection to entanglement measures.Phys. Rev.
A 68, 012111 (2003).
46
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
R.A. Bertlmann, W. Grimus and B.C. Hiesmayr: Quantum mechanics,
Furry's hypothesis and a measure of decoherence. Phys. Rev. D 60, 114032
(1999).
A. Bramon, G. Garbarino and B.C. Hiesmayr: Quantum marking and
quantum erasure for neutral kaons. Phys. Rev. Lett. 92,020405 (2004)
A. Bramon, G. Garbarino and B.C. Hiesmayr.: Active and pas- sive quantum
eraser for neutral kaons. Phys. Rev. A 69, 062111 (2004).
B.C. Hiesmayr and M. Huber: Bohr's complementarity relation and the
violation of the CP symmetry in high energy physics. Physics Letters A, 372
(20), 3608 (2008).
A. Bramon, G. Garbarino and B.C. Hiesmayr.: Quantitative complementarity
in two-path interferometry, Phys. Rev. A 69, 022112 (2004).
G. Amelino-Camelia et.al: Physics with the KLOE-2 experiment at the
upgraded DAPHNE. Accepted by Physical Journal C or arXiv:1003.3868.
M. Huber, F. Mintert, A. Gabriel and B.C. Hiesmayr. Detection of highdimensional qenuine multi-partite entanglement of mixed state. Phys. Rev.
Lett. 104, 210501 (2010).
N. Friis, R.A. Bertlmann, M. Huber, B.C. Hiesmayr. Relativistic entanglement
of two massive particles. Phys. Rev. A81, 042114 (2010)
AMP-5 HS 414, Do, 9 Sept. 2010, 13:30 Uhr
Electron Spin Resonance in Doped Helium Nanodroplets as Tool to
Study Magnetic Properties and Spin Dynamics
M. Ratschek1, M. Koch1,*, J. Poms1, A. Volk1, C. Callegari1,2, and W. E. Ernst1
1
Institute of Experimental Physics, TU Graz, Petersgase 16, 8010 Graz, Austria
Sincrotrone Trieste, Strada Statale 14 – km 163.5, 34149 Basovizza, Trieste, Italy
*Corresponding author: [email protected]
2
Superfluid helium (He) nanodroplets provide a versatile substrate to isolate and
cool (0.38 K) single atoms and molecules and, if desired, assemble weakly
bound complexes. Electron spin resonance (ESR) is a versatile probe of the
electronic environment in radicals and, via spin tags, also in ESR-silent species.
We have recently achieved ESR of single alkali-metal atoms isolated on He
nanodroplets [1,2,3]. The influence of the droplet on the alkali-metal
valence-electron wave function is directly noticeable as a shift of the ESR
transitions with respect to that of free atoms. This perturbation depends on the
size of the droplets and can be modeled with an increase of the hyperfine
constant, that is, an increase of the Fermi contact interaction.
After a careful characterization of the Rb-He-droplet system the method is
currently being developed into a more universal diagnostic tool to study
magnetic properties and spin dynamics. We believe that ESR-silent species
located inside the droplet can be investigated by utilizing the surface Rb atom
47
as spin label, and the droplet size will be a convenient handle to control the
distance between the two. We are also extending our method to study
magnetically active materials of technological importance, such as Cr, Cu, and
small clusters thereof.
References
[1]
Koch, M., Auböck, G., Callegari, C., and Ernst, W.E., “Coherent Spin
Manipulation and ESR on Superfluid Helium Nanodroplets”, Phys. Rev. Lett.
103(3), 035302–1–4(2009)
[2]
Koch, M., Lanzersdorfer, J., Callegari, C., Muenter, J.S., and Ernst, W.E.,
“Molecular Beam Magnetic Resonance in Doped Helium Nanodroplets. A
Setup for Optically Detected ESR/NMR in the Presence of Unresolved
Zeeman Splittings.”, JPC A 113, 13347 (2009)
[3]
Koch, M., Callegari, C., and Ernst, W.E., “Alkali-metal electron spin density
shift induced by a helium nanodroplet”, Mol. Phys. 108, 1008 (2010)
AMP-6 HS 414, Do, 9 Sept. 2010, 14:00 Uhr
Contrast Measurements of CPT resonances Formed
on the 87Rb D1 and D2 Line
M. Ellmeier1, R. Lammegger1 and L. Windholz1
1
Institute of Experimental Physics, Graz University of Technology, Petersgasse 16,
8010 Graz, [email protected]
We present investigations on contrast measurements of Coherent Population
Trapping (CPT) resonances used to improve the noise performance of a new
compact Coupled Dark State Magnetometer (CDSM).
CPT can be understood as a quantum interference effect, which occurs in an
atomic three level excitation system in the simplest case. The CPT resonances
- representing so called dark states - can obtain line widths of about 30 Hz
(about seven orders of magnitude smaller than the width of the optical
transition), therefore this phenomenon can be used for precision
measurements.
In our experiment several three level excitation systems are established via a
modulated vertical-cavity surface-emitting laser within the hyperfine structure of
the 87Rb D1 and D2 lines. In our setup the contrast of the CPT resonances for
the excitation of the D 1 and D2 line is determined by an indirect contrast
measurement method well-suited for small CPT resonance amplitudes with low
signal-to-noise ratio.
We report an increase of the contrast for the excitation of the D1 line compared
to the D2 line. This is mainly caused by a different number of hyperfine levels
contributing to the excitation process. In our case the excited state 5 2P1/2 of the
48
D1 line has half of hyperfine levels compared to the excited state 52P3/2 of the
D2 line. In the latter case not all excited state levels contribute to the
preparation of the CPT resonances. Those levels, being not involved in the CPT
resonance creation, will lead to a decreased excitation efficiency of the atomic
level population into the dark states. As a consequence, in the case of the D2
line excitation the contrast of the CPT resonances is reduced significantly.
For this reason the D1 line excitation is preferable in applications like compact
CPT atomic clocks and magnetometers.
AMP-7 HS 414, Do, 9 Sept. 2010, 14:15 Uhr
Ab Initio Spin Densities of Small Alkali-Metal Doped Helium Droplets
T. Gruber, A. W. Hauser and W. E. Ernst
Institute of Experimental Physics, Graz University of Technology,
Petersgasse 16, A-8010 Graz, Austria, [email protected]
In recent experiments of our group on alkali-metal-doped helium droplets, it could
be shown that the hyperfine structure of the dopants is strongly affected by the
helium surrounding. [1] A change of the hyperfine splitting of 39K is observed as a
function of the nozzle temperature, indicating a dependence on the helium droplet
size. Hence we started a theoretical investigation based on an open shell coupled
cluster approach to study this size effect within molecular orbital theory.
In our theoretical model we are restricted to very small HeNX clusters (N=15,X=Li,Na,K) due to the high computational demands of the chosen method.
However, it is possible to identify two antagonistic effects of the helium surrounding
on the electronic wavefunction of the alkali dopant: The first effect is a compression
of the wavefunction which leads to higher spin densities |)0|2 at the core, the
second one is a reduction of |)0|2 due to the Pauli repulsion, i.e. the deformation of
the s-orbitals.
Despite of the computational limitations we also try to give estimations for larger
systems. Here we apply a combination of the quantum chemistry approach with a
stochastic geometry optimization. Assuming only two-body-interactions we use the
simulated annealing technique to obtain geometry predictions.
References
[1]
Koch, M., Auböck, G., Callegari, C., Ernst, W. E., “Coherent spin
manipulation and ESR on superfluid helium nanodroplets”,
Physical Review Letters 103(3), 035302–1–4(2009)
49
AMP-8 HS 414, Do, 9 Sept. 2010, 14:30 Uhr
Towards the Generation of Entangled Photon Pairs in Microcavities
P. Cristofolini, Z. Vörös and G. Weihs
Photonik Gruppe, Institut für Experimentalphysik, Universität Innsbruck
Technikerstrasse 25d, A-6020 Innsbruck, Österreich
E-Mail: [email protected]
Quantum wells (QWs) placed at the antinodes of a semiconductor microcavity are
an interesting system to study light-matter interactions and cavity QED in a solid
state environment. Because of their small size and the ease of incorporating them
into integrated optics setups, semiconductor microcavities can be used as an
efficient, small and fast source of entangled photons [1] for quantum computation
and cryptography.
In the strong coupling regime of quantum well excitons and cavity photons, the
system can be described as consisting of polaritons, new quasiparticles with
interesting properties. Several schemes have been proposed to generate entangled
photons [2] using polariton-polariton scattering. All of them require a good control of
the excitation laser's parameters.
We built a new experimental apparatus using a spatial light modulator (SLM) to
steer one or multiple beams without moving any mechanical parts. In this way we
can precisely control the excitation angle, its spot size and position on the sample.
In the future we will perform state tomography in order to measure the degree of
entanglement of the generated pairs.
References
[1] W. Langbein, Polariton “Correlation in microcavities produced by parametric
scattering”, Phys. Stat. Sol., 242(11):2260_2270, July 2005.
[2] C. Ciuti, “Branch-entangled polariton pairs in planar microcavities and photonic
wires”, Phys. Rev. B, 69(24):245304, Jun 2004.
AMP-9 HS 414, Do, 9 Sept. 2010, 14:45 Uhr
Photoionization of Rb Atoms on He Nanodroplets
F. Lackner 1, M. Theisen¹, and W. E. Ernst1
1
Institute of Experimental Physics, Graz University of Technology,
Petersgasse 16, Graz, 8010, Austria, [email protected]
Ionization experiments of Rb doped onto superfluid He nanodroplets are presented.
Rb atoms on the surface of helium droplets were photoionized by means of one
2
2
photon ionization, and via resonant two step ionization (with the 5 P1/2 and 5 P3/2
state as intermediate states). The two step ionization has the advantage of being
50
selective for Rb monomers. The Rb atom in the 52P1/2 state remains on the droplet
while the one in the 52P3/2 state detaches from the droplet [1].
The ionization products were monitored with a time-of-flight mass spectrometer. At
low masses the formation of Rb+-HeN (N<20) complexes was observed except in
2
the case of two step ionization via the 5 P1/2 state. The detection of very high
masses, up to several thousand amu, indicates the formation of stable Rb+-HeN
(e.g., N=1500) complexes. We conclude therefore that the Rb+ is immersed in the
He droplet subsequently to the ionization process.
References
[1]
Auböck, G., Nagl, J., Callegari, C., Ernst, W.E.,”Electron Spin Pumping of
Rb Atoms on He Nanodroplets via Nondestructive Optical Excitation”,
Physical Review Letters 101, 035301 (2008)
AMP-10 HS 414, Do, 9 Sept. 2010, 15:00 Uhr
Plasma Generation by Combination of Two Laser Wavelengths
E. Schwarz, G. A. Reider, A. Kremsner and E. Wintner
Photonics Institute, Vienna University of Technology,
Gusshausstrasse 25-29, 1040 Wien, Austria
Engine concepts of the future have to aim for an increase in efficiency going along
with a simultaneous reduction of detrimental exhaust components (CO, CHx, NOx
and soot). One promising idea to reach these goals is the concept of laser-induced
ignition for combustion engines. Generally, a laser-ignition system offers a multitude
of advantages e.g. the probability to ignite leaner mixtures is higher. As a
consequence of the high leanness of the mixtures, the flame temperature is lowered
and hence also the NOx-emissions, whereas the efficiency of the engine can be
increased. For electric spark ignition the spark voltage has to be raised with
increasing pressure, which causes stronger erosion of the electrodes. Laser ignition
systems do not require electrodes and hence maintenance costs of a laser ignition
system are expected to be significantly lower than those of a spark plug system [1].
Customary lasers are, because of their overall size and high initial costs, only
applicable for laboratory test rigs and cannot fulfill the needs of an ignition laser.
Therefore, it was necessary to develop a compact and robust ignition laser by
ourselves which can deliver the pulse energy required to ensure reliable ignition.
The outcome was a compact high peak power, passively Q-switched, longitudinally
diode-pumped solid-state laser [2]. The next challenge will be to optimize the laser
system in regard of efficiency and costs.
51
To improve the laser system systematic studies to reduce the laser pulse energy for
plasma generation (MPE) were achieved. The influence of the laser wavelength on
the plasma formation has been studied extensively in previous experimental and
theoretical studies [3]. Summarized briefly, a shorter wavelength can be focused to
a smaller spot size which reduces the threshold for plasma formation while the
plasma absorption for a longer wavelength is much better.
With a coherent superposition of an infrared-laser pulse and its second harmonic,
the threshold of plasma formation as well as the energy transfer efficiency from the
laser field to the plasma can be significantly improved in comparison to purely
monochromatic radiation.
The first time we present experimental results concerning coherence effects in two
color laser plasma generation in air at atmospheric pressure.
References
[1]
H. Kopecek, E. Wintner, M. Lackner, F. Winter, and A. Hultqvist, LaserStimulated Ignition in a Homogeneous Charge Compression Ignition
Engine. SAE SP. 1819, 183 (2004).
[2]
H. Kofler, J. Tauer, G. Tartar, K. Iskra, J. Klausner, G. Herdin, and E.
Wintner, An Innovative solid-state laser for engine ignition. Laser Physics
Letters. 4(4), 322 (2006).
[3]
L.J. Radziemski and D.A. Cremers, Laser-Induced Plasmas and
Applications. 1 ed. Optical Engineering, ed. B.J. Thompson (Marcel
Dekker Inc., New York, 1989).
AMP-11 HS 414, Do, 9 Sept. 2010, 15:15 Uhr
A Composite Parameterization of Unitary Groups,
Density Matrices and Subspaces
Ch. Spengler, M. Huber and B. C. Hiesmayr
Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria
[email protected],
[email protected],
[email protected]
Many quantities in quantum physics are related to optimization problems that
necessitate to vary over the set of all unitary transformations, density matrices or
subspaces. Problems of this kind arise, for instance, in the field of quantum
information in the detection, classification and quantification of entanglement (see
[1, 2, 3] and references therein), finding optimal measurement settings for quantum
states with respect to Bell inequalities [4, 5] and the study of (n-copy) distillability [6,
7]. All these tasks can be considerably simplified by using adequate
parameterizations of the central objects. Here we introduce a non-redundant
composite parameterization [8] of the unitary group U(d) for arbitrary dimension d
52
whose building blocks are matrix exponential functions of generalized antisymmetric sigma-matrices and one-dimensional projectors. The specific form of this
parameterization has several advantages with respect to numerical tractability and
the identification of irrelevant parameters concerning a vast number of problems. It
enables us to formulate redundancy-free density matrices of arbitrary rank k.
Furthermore, we show how the parameterization can be used to construct and
cover all k-dimensional orthonormal subspaces of C^d with the minimal number of
parameters. As an example it will be shown that this feature paves the way for
numerically investigating distillability of high-dimensional quantum systems.
References
[1] Gühne O. and Tóth G., “Entanglement detection”, Physics Reports 474,
1 (2009)
[2] Horodecki R., Horodecki P., Horodecki M. and Horodecki K., “Quantum
entanglement“, Rev. Mod. Phys. 81, 865 (2009)
[3] Huber M., Mintert F., Gabriel A. and Hiesmayr B.C., “Detection of highdimensional genuine multi-partite entanglement of mixed states”, Phys. Rev.
Lett. 104, 210501 (2010)
[4] Son W., Lee J., and Kim M.S., “d-outcome measurement for a nonlocality
test”, J. Phys. A: Math. Gen. 37, 11897 (2004)
[5] Spengler Ch., Huber M., and Hiesmayr B.C., “On the state space geometry
of the CGLMP-Bell inequality”, arXiv:0907.0998 (2009)
[6] Horodecki M., Horodecki P., and Horodecki R., “Mixed-State Entanglement
and Distillation: Is there a “Bound” Entanglement in Nature?”, Phys. Rev.
Lett. 80, 5239 (1998)
[7] Dür W., Cirac J.I., Lewenstein M. and Bruss D., “Distillability and partial
transposition in bipartite systems”, Phys. Rev. A 61, 062313 (2000)
[8] Spengler Ch., Huber M. and Hiesmayr B.C., “A composite parameterization
of unitary groups, density matrices and subspaces”, arXiv:1004.5252 (2010)
53
8.4 FAKT (KTP) – Fachausschuss Kern- und Teilchenphysik
Parallel Session FAKT (Topic LHC)
Zeit
Time
Vortragender
Lecturer
Vortragstitel
Title of Lecture
9:00 9:10
Kajetan Fuchsberger
(CERN)
Status of the LHC beam commissioning
9:10 9:20
Franz Mittermayr
(HEPHY ÖAW)
Status of the CMS experiment at CERN
9:20 9:30
Christian Thomay
(HEPHY ÖAW)
Commissioning of the b-jet identification
in CMS
9:30 9:40
Edmund Widl
(HEPHY ÖAW)
Preparation for supersymmetry searches
at CMS:
Jets and missing energy
9:40 9:50
Thomas Bergauer
(HEPHY ÖAW)
Operation of the CMS Tracker at the
Large Hadron Collider
9:50 10:00
Valentin Knünz
(HEPY ÖAW)
Measurement of quarkonium production
at CMS
10:00 10:10
Erik Huemer
(HEPHY ÖAW)
Upgrade of the CMS tracker for hHigh
luminosity operation
10:10 10:20
Elmar Ritsch
(Univ. Innsbruck)
Simulation of Calorimeter Punch –
Through Particles in ATLAS
54
10:20 10:30
Patrick Jussel
(Univ. Innsbruck)
First observations of J/\+ and D(*)
mesons in pp collisions at s = 7 TeV
in the ATLAS experiment
10:30 10:40
Wolfgang Kiesenhofer
(HEPHY ÖAW)
Muon reconstruction for SUSY searchers
at CMS
11:00 11:30
Fachausschuß Kern- und Teilchenphysik Scientific Committee Nuclear and Particle Physics (FAKT)
Parallel Session FAKT (Topic Theory)
Zeit
Time
Vortragender
Lecturer
Vortragstitel
Title of Lecture
13:30 13:50
Reinhard Alkofer
(Univ. Graz)
On baryon properties from QCD
bound-state equations
13:50 14:00
Beatrix Hiesmayr
(Univ. Wien)
Testing foundations of quantum mechanics
in particle physics
14:00 14:10
Marcus Huber
(Univ. Wien)
Detection and classification of genuine
multipartite entanglement in highdimensional mixed states
14:10 14:20
Andreas Krassnigg
(Univ. Graz)
Toward a comprehensive meson
spectroscopy with the Bethe-Salpeter
equation
14:20 14:30
Martina Blank
(Univ. Graz)
From (in)homogeneous Bethe-Salpeter
amplitudes to observables
55
14:30 14:40
Sabine Ertl
(TU Wien)
All stationary axi-symmetric solutions to
topologically massive gravity
14:40 14:50
Branislav Cvetkovi
(Institute of Physics,
Belgrade)
Canonical structure of new massive gravity
14:50 15:00
Harold Steinacker
(Univ. Wien)
Emergent Geometry and Gravity from
Yang-Mills Matrix Models
CANCELLED
15:00 15:10
Wolfgang
Waltenberger
(HEPHY ÖAW)
Towards a description of physics beyond
the standard model with on-shell
effective theories
15:30 16:00
Parallel Session FAKT (Topic Plan)
16:30 - 16:45
Michael Benedikt
(CERN)
Status of the MedAustron Project
16:45 - 17:00
Christian Fabjan
(TU Wien)
The Physics Cluster for Atomic and
Subatomic Physics
Jahreshauptversammlung des
Fachausschusses FAKT
FAKT Annual General Assembly
17:00 18:00
18:30 20:00
Robert Schöfbeck
(HEPHY ÖAW)
Sterne - Kerne – Teilchen
Eine Reise von den kleinsten Teilchen bis
zu den Grenzen des Weltalls auf der der
Suche nach der neuen Physik
56
Freitag - Friday 10 September 2010 / Audi Max
Parallel Session FAKT (Topic Experiment)
Zeit-Time
9:00 9:20
Olaf Hartmann
(SMI ÖAW)
The FOPI Experiment at GSI-SIS
9:20 9:30
Tobias Jenke
(TU Wien)
Rabi spectroscopy and excitation in a
gravity cavity of neutron matter waves
9:30 9:40
Xiangzun Wang
(TU Wien)
Standard model tests with PERC
9:40 9:50
Barbara Wünschek
(SMI ÖAW)
Status and plans of experiment E17 at
J-PARC
9:50 10:00
Claudia Lederer
(Univ. Wien)
New measurement of the 62Ni(n,J) crosssection with n_TOF at CERN relevant for
the astrophysical s-process
10:00 10:10
Klaus Mair
(Univ. Wien)
Developments towards Radiocarbon Dating
of ultra-small DNA samples
10:10 10:20
Martin Martschini
(Univ. Wien)
Recent advances in AMS of 36Cl with
a 3-MV-Tandem
10:20 10:30
Oswald Massiczek
(SMI ÖAW)
A new cryogenic target and microwave
cavity for hyperfinestructure spectroscopy
of antiprotonic helium
10:30 10:40
Susanne Friedreich
(SMI ÖAW)
Hyperfine structure spectroscopy
with antiprotonic helium
57
10:40 10:50
Stefan Pavetich
(Univ. Wien)
AMS measurement of the reaction
35
Cl(n,J)36Cl and its relevance to
astrophysics and nuclear technology
11:00 11:30
Parallel Session FAKT (Topic Detector + Software)
11:30 11:40
11:40 - 11:50
Wolfgang Frisch
(HEPHY ÖAW)
HFOLD a program package for calculating
MSSM two-body Higgs decays at full
one-loop level
Using Vienna Tier-2 Grid computing for data
Natascha Hörmann analysis of the CMS experiment and for other
research projects
11:50 - 12:00
Robert Fröschl
(CERN)
JEREMY – a code for radiological
characterization of accelerator components
at CERN
12:00 - 12:10
Denise Neudecker
(TU Wien)
GENEUS - A program designed for
nuclear data evaluations
12:10 - 12:20
Gamal Ahmed
(SMI ÖAW)
Silicon photomultiplier for subatomic
physics experiments
- performance studies at SMI
12:20 - 12:30
Imanuel Gfall
(HEPHY ÖAW)
Belle II silicon vertex detector: mechanics
and cooling
12:30 - 12:40
Jürgen Pfingstner
(CERN)
Ground motion mitigation in the main linac
of CLIC
12:40 12:50
Philipp Müllner
(SMI ÖAW)
Gem detector development for
hadron-physics experiments
12:50 - 13:30
FAKT Fachtagung Zusammenfassung
FAKT Session Summary
58
FAKT-1 Audi Max: 9 Sept. 2010, 9:00 Uhr
Status of LHC Beam Commissioning
K. Fuchsberger
CERN, 1211 Genève 23, Switzerland, BE-OP-SPS, [email protected]
After the incident on the 19th September 2008 and more than one year without
beam the commissioning of the LHC started again on November 20, 2009.
Progress was rapid and collisions under stable beam conditions were established at
1.2 TeV within 3 weeks. In 2010 after qualification of the new quench protection
system the way to 3.5 TeV was open and collisions were delivered at this energy
after a month of additional commissioning. Currently commissioning for unsafe
beams is in progress. Intensity increase will be done in steps, each of them followed
by an extended running period.
We describe the experiences and issues encountered during these first periods as
well as the current status of commissioning with beam.
FAKT-2 Audi Max: Do, 9 Sept. 2010, 9:10 Uhr
Status of the CMS Experiment at CERN
F. Mittermayr1, CMS Collaboration2
1
Institute of High Energy Physics of the Austrian Academy of Sciences
Nikolsdorfer Gasse 18, 1050 Vienna, Austria
[email protected]
2
CERN, 1211 Geneva 23, Switzerland
The Large Hadron Collider (LHC) at CERN is now in operation and providing steady
particle beams at an energy of 3.5 TeV giving CMS the chance to observe already
known phenomena as well as enabling early searches for new physics. The CMS
collaboration has already published papers on real collision data.
This talk will give an overview of the latest developments in CMS’ operation,
performance and the results already achieved at half the LHC design energy by the
physics teams.
59
Commissioning of the b-jet Identification in CMS
C. Thomay
Institut for High Energy Physics, Austrian Academy of Sciences
Nikolsdorfer Gasse 18, A-1050 Wien
[email protected]
The identification of jets containing products of the decay of a B-hadron is a key
component in the analysis of proton-proton-collisions at the LHC, both for
measurements in the framework of the standard model and for searches for New
Physics. First data recorded by the CMS experiment have been used to compare
the distributions of observables used in the identification, such as impact
parameters of tracks and reconstructed decay vertices, with the expectations from
simulation. Preliminary measurements of the performance of the algorithms in terms
of efficiency and mis-identification rates are also shown.
Preparation for Supersymmetry Searches at CMS: Jets
and Missing Energy
E. Widl1 and R. Schöfbeck2
Institute of High Energy Physics of the Austrian Academy of Sciences
Nikolsdorfer Gasse 18, A-1050 Vienna, Austria
1
[email protected],
2
[email protected]
Searches for supersymmetry [1] have to deal with a broad range of signatures on
top of a large variety of background processes with cross-sections expected to be
some orders of magnitude bigger than the actual signal. Therefore one requires a
good understanding of the corresponding physics observables and careful control
over backgrounds from standard model processes. For this purpose the first protonproton collision data at a center-of-mass energy of 7 TeV recorded by the CMS
experiment [2] have been used to study the performance of the reconstruction of
jets and missing energy [3,4]. The methods developed for data-driven background
estimation have been tested to study QCD backgrounds and to validate predictions
of background distributions [5]. All results have been compared with predictions
from simulation.
References
[1]
Martin, S., “A Supersymmetry Primer”, arXiv:hep-ph/9709356v5
[2]
CMS Collaboration, “The CMS Experiment at the CERN LHC”, JINST 3,
60
[3]
[4]
[5]
S08004 (2008)
CMS Collaboration, “CMS Jet Performance in pp Collisions at s = 7 TeV”,
CMS Physics Analysis Summary, CMS PAS JME-10-003
CMS Collaboration, “CMS MET Performance in Jet Events from pp
Collisions at s = 7 TeV”, CMS Physics Analysis Summary, CMS PAS JME10-004
CMS Collaboration, “Performance of Methods for Data-Driven Background
Estimation for SUSY Searches in the CMS Experiment”, CMS Physics
Analysis Summary, CMS PAS SUS-10-001
Operation of the CMS Tracker at the Large Hadron Collider
W. Adam, T. Bergauer, M. Dragicevic, M. Friedl, R. Frühwirth, St. Hänsel,
M. Hoch, J. Hrubec, M. Krammer, M. Pernicka, E. Widl
Institut für Hochenergiephysik der ÖAW, Nikolsdorfer Gasse 18, 1040 Wien
[email protected]
The inner tracking detector of the Compact Myon Solenoid (CMS) Experiment at
CERN is the largest semiconductor tracking device built so far. It consists of more
than 25,000 individual silicon sensors with a total active area of almost 200 square
meters. Its design, construction and commissioning was a huge effort of more than
50 institutes around the world and lasted almost seven years. The institute of High
Energy Physics (HEPHY) of the Austrian Academy of Sciences contributed
significantly to this project since its beginning by working on both the silicon strip
and the pixel detectors.
With the start of normal operation of the Large Hadron Collider (LHC), the CMS
Tracker became operational as a scientific device and as part of the CMS
experiment during data taking. Operation experience is gained continuously as the
LHC delivers proton-proton collisions. In this presentation all critical systems of the
tracker will be summarized and performance data will be presented. These
numbers will show that both, the tracker and the whole experiment are working
extremely well. First physics plots are already emerging, like measurements of the
masses of different well-known particles. These measurements are helpful in
calibrating the detector to be well prepared for the discovery of new physics as the
LHC continues to deliver collision data.
61
Measurement of Quarkonium Production at CMS
V. Knünz
Institut of High Energy Physics, Austrian Academy of Sciences
Nikolsdorfer Gasse 18, A-1050 Vienna
Since early 2010 the CMS experiment is recording proton-proton collisions at the
yet unexplored energy of 7 TeV. This talk presents the first measurements of J/Psi
and Upsilon production at this energy. The techniques used for event selection and
reconstruction are shown and an outlook on future measurements with quarkonia
states will be given.
Upgrade of the CMS Tracker for High Luminosity Operation
G. Auzinger, M. Bernard-Schwarz, T. Bergauer, M. Dragicevic, M. Friedl,
S. Hänsel, E. Huemer1, J. Hrubec and M. Krammer
1
[email protected]
The CMS experiment is one of the four large experiments which are currently
carried out at the Large Hadron Collider (LHC) at CERN. The innermost
detector system, the so-called tracker, is performing with high efficiency and
delivers an important contribution to the reconstruction of the physics processes
governing the collision of protons with a center-of-mass energy of 14 TeV.
An upgrade of the accelerator is planned around 2020, which will boost the
luminosity by a factor of ten and will cause a significant increase of the
interaction rate. In turn, this will also increase the number of background
interactions which has significant impact on the performance of the system to
select interesting events (the trigger) and the tracker.
To cope with the larger number of particles per collision, the number of sensor
elements in the tracker has to be increased while reducing the overall material
budget of the detector system. Furthermore, the lifetime of the current tracker is
already limited by the harsh radiation environment in the center of the detector
to 10 years of operation at the current design luminosity. For the subsequent
operation of a new tracker at high luminosity, entirely new sensor materials are
needed, which are able to withstand the tenfold increase in irradiation.
The Institute of High Energy Physics (HEPHY) is significantly involved in the
research and development of the new CMS tracker for high luminosity
62
operation. This talk will give a short introduction on the main challenges for the
new detector, followed by a presentation of the newest developments on silicon
strip sensors which are designed and investigated at HEPHY.
Simulation of Calorimeter Punch-Through Particles in ATLAS
E. Ritsch1, A. Salzburger2 and E. Kneringer1
1
Universität Innsbruck, Institut für Astro- und Teilchenphysik
Technikerstrasse 25, 6020 Innsbruck, [email protected]
2
CERN, 1211 Geneva 23, Switzerland
In the ATLAS detector the electromagnetic and hadronic calorimeters should
confine any strongly interacting particle type. Therefore mostly muons pass through
the calorimeters and create signals in the muon system (MS).
Due to interactions in the calorimeters, there is a certain probability that any high
energetic particle (other than a muon) creates child-particles which have enough
energy to leave the calorimeter and enter the MS. These so called punch-through
particles will then create signals in the MS which can be misinterpreted as signals
coming form muons originating from the proton-proton interaction point.
This effect is studied with full Geant4 Monte Carlo simulations and a parametrised
and simplified model is implemented in FATRAS which is a fast ATLAS simulation
software.
First Observations of J/\+ and D(*) Mesons in
pp Collisions at s = 7 TeV in the ATLAS Experiment
P. Jussel, E. Kneringer and D. Kuhn
Universität Innsbruck, Institut für Astro- und Teilchenphysik
Technikerstrasse 25, 6020 Innsbruck
[email protected]
In the ATLAS [1] detector at the LHC the decay channel J/\ + is measured [2]
using proton-proton collisions at a centre of mass energy of s = 7 TeV. The
resonance and the combinatorial background are fitted using an unbinned
maximum likelihood method. The reconstructed invariant mass and peak width are
compatible with PDG world-average values as well as Monte Carlo expectations.
The kinematic properties of the J/\ and trigger efficiencies are presented.
63
In addition, hadronic decays of D*±, D(±) and Ds± mesons are reconstructed [3] at the
ATLAS using the same dataset. Also those measurements are in good agreement
with the PDG values.
References
[1]
The ATLAS Collaboration; Expected performance of the ATLAS experiment :
detector, trigger and physics; arXiv:0901.0512, CERN-OPEN-2008-020
(2008).
[2]
The ATLAS Collaboration; First observation of J/\ + resonance in the
ATLAS pp collisions at s = 7 TeV; submitted for CONF Notes for
PLHC2010 (2010).
[3]
The ATLAS Collaboration; D(*) meson reconstruction in pp collisions at s =
7 TeV; submitted for CONF Notes for PLHC2010 (2010).
Muon Reconstruction for SUSY Searches at CMS
W. Kiesenhofer
Institut of High Energy Physics, Austrian Academy of Sciences
Nikolsdorfer Gasse 18, A-1050 Vienna
Searches for supersymmetry (SUSY) involve a broad range of signatures including
events featuring isolated muons. Studying those decay channels has the advantage
that the dominating standard model QCD background can be relatively well
suppressed. Nonetheless a careful evaluation of muon reconstruction is necessary
that involves the measurement of detection and trigger efficiencies as well as muon
fake rates, which pose a major contribution to the background.
This talk gives an overview about the specific way CMS measures muons and
summarizes several methods used to estimate efficiencies and fake rates as well as
results from their application on first data.
On Baryon Properties from QCD Bound-State Equations
H. Sanchis Alepuz1, R. Alkofer1, S. Villalba Chavez1 and Gernot Eichmann2
1I
Inst. Physics, Graz University, 8010 Graz, Austria; [email protected]
Inst. Nuclear Physics, TU Darmstadt, D 64289 Darmstadt, Germany
2
64
Employing an approach based on the Green functions of Landau-gauge QCD
some selected results from calculations of baryon properties are presented.
Hereby a rainbow-ladder truncation to the quark Dyson-Schwinger equation is
used to arrive at an unified description of mesons and baryons by solving
Bethe-Salpeter and covariant Faddeev equations, respectively, see [1,2] and
references therein.
References
[1]
G. Eichmann, R. Alkofer, A. Krassnigg, D. Nicmorus, “Nucleon mass from a
covariant three-quark Faddeev equation”, Phys. Rev. Lett. 104 (2010)
201601 [arXiv: 0912.2876 [hep-ph]]
[2]
G. Eichmann, “Hadron properties from QCD bound-state equations”, Ph.D.
Thesis, University of Graz [arXiv:0909.0703[hep-ph]]
Testing Foundations of Quantum Mechanics in Particle Physics
T. Adaktylos1, A. Gabriel1, B.C. Hiesmayr12, F. Hipp1, M. Huber1, G. Krizek1,
S. Radic1, H. Schimpf1, Ch. Spengler1 and H. Waldner1
1
University of Vienna, Faculty of Physics, Botzmanngasse 5, A-1090 Vienna
University of Sofia, Faculty of Physics, Blvd. James Bourchier 5, 1164 Sofia,
Bulgaria
2
Particle physics has become an interesting testing ground for questions of
foundations of quantum mechanics. Entangled massive meson-antimeson systems
are specially suitable as they offer a unique laboratory to test various aspects of
particle physics (CP violation, CPT violation,. . . ) as well to test foundations of
quantum mechanics, e.g. Bell inequalities [1, 2, 3, 4], decoherence effects [5, 6],
quantum marking and erasure concepts [7, 8], Bohr's complementary relation [9,
10]. The main aim of this talk is to show that these systems not consisting of
ordinary matter and light provide novel insights into quantum theory. Particularly, we
show that a certain Bell inequality is related to the observed tiny difference between
matter and antimatter [3, 4], the so called CP violation explored in particle physics.
Herewith two different powerful concepts in physics, entanglement or its
manifestation and symmetry, become related. Then we show a Bell inequality
sensitive to the quantum number strangeness [3], which is not violated for the
maximally entangled spin singlet state, but surprisingly for a non-maximally
entangled state [1]. This opens for the first time the possibility of a direct
experimental. We will shortly discuss the status quo of the realization [11] with the
upgraded KLOE detector (DAPHNE machine, Italy). In summary, understanding the
nature of entanglement and its manifestation needs also studies of entanglement at
different energy scales and as recent works show there are still many open
questions concerning entanglement, e.g. about high dimensional genuine
65
multipartite entanglement [12] or of relativistic entanglement of massive spin 1/2
particles [13].
References
[1]
B.C. Hiesmayr: Nonlocality and entanglement in a strange system.European
Physical Journal C, Vol. 5073-79 (2007).
[2]
B.C. Hiesmayr: A generalized Bell inequality and decoherence for the K0
anti-K0 system. Found. of Phys. Lett. 14, 231 (2001).
[3]
R.A. Bertlmann and B.C. Hiesmayr: Bell inequalities for entangled kaons
and their unitary time evolution. Phys. Rev. A 63, 062112 (2001).
[4]
R.A. Bertlmann, W. Grimus and B.C. Hiesmayr: Bell inequality and CP
violation in the neutral kaon system. Phys. Lett. A 289, 21 (2001).
[5]
R.A. Bertlmann, K. Durstberger and B.C. Hiesmayr.: Decoherence of
entangled kaons and its connection to entanglement measures.Phys. Rev. A
68, 012111 (2003).
[6]
R.A. Bertlmann, W. Grimus and B.C. Hiesmayr: Quantum mechanics,
Furry's hypothesis and a measure of decoherence. Phys. Rev. D 60, 114032
(1999).
[7]
A. Bramon, G. Garbarino and B.C. Hiesmayr: Quantum marking and
quantum erasure for neutral kaons. Phys. Rev. Lett. 92,020405 (2004)
[8]
A. Bramon, G. Garbarino and B.C. Hiesmayr: Active and pas- sive quantum
eraser for neutral kaons. Phys. Rev. A 69, 062111 (2004).
[9]
B.C. Hiesmayr and M. Huber: Bohr's complementarity relation and the
violation of the CP symmetry in high energy physics. Physics Letters A, 372
(20), 3608 (2008).
[10] A. Bramon, G. Garbarino and B.C. Hiesmayr.: Quantitative complementarity
in two-path interferometry, Phys. Rev. A 69, 022112 (2004).
[11] G. Amelino-Camelia et.al: Physics with the KLOE-2 experiment at the
upgraded DAPHNE. Accepted by Physical Journal C or arXiv:1003.3868.
[12] M. Huber, F. Mintert, A. Gabriel and B.C. Hiesmayr. Detection of highdimensional qenuine multi-partite entanglement of mixed state. Phys. Rev.
Lett. 104, 210501 (2010).
[13] N. Friis, R.A. Bertlmann, M. Huber, B.C. Hiesmayr. Relativistic entanglement
of two massive particles. Phys. Rev. A81, 042114 (2010)
Detection and Classification of Genuine Multipartite Entanglement
in High-Dimensional Mixed States
M. Huber1, Andreas Gabriel2 and Beatrix Hiesmayr3
1
University of Vienna, Boltzmanngasse 5, A1090 Vienna,
[email protected]
2
3
66
We present a general framework to identify genuinely multipartite entangled mixed
quantum states in arbitrary-dimensional systems and show on exemplary cases that
the constructed criteria are stronger than previously known ones. Our criteria are
simple inequalities involving matrix elements of the given quantum state and detect
genuine multi-partite entanglement that had not been identified so far. They are
experimentally accessible without quantum state tomography and are easily
computable as no optimization or eigenvalue evaluation is needed. We also provide
an optimal way for constructing the observables needed to identify the separability.
Also we show that with such inequalities it is possible to distinguish certain classes
of genuinely multipartite entangled states, e.g. the GHZ and W class. Furthermore
these criteria prove to be versatile tools for detecting separability with respect to
different partitions of multipartite states and provide novel ways of deriving lower
bounds on concurrence based entanglement measures. In the end we show how
with the help of such a framework, one can go further and not only identify genuine
multipartite entanglement, which is constituted by non-2-separability, but generalize
it to achieve criteria for non-k-separability in arbitrary dimensional multipartite
states.
References
[1]
M. Huber, F.Mintert, A. Gabriel and B.C. Hiesmayr, „Detection of HighDimensional Genuine Multipartite Entanglement of Mixed States“, Phys.
Rev. Lett. 104, 210501 (2010)
[2]
A. Gabriel, B.C. Hiesmayr and M, Huber, „Criterion for k-separability in
mixed multipartite systems“, arXiv/quant-ph: 1002.2953
Toward a Comprehensive Meson Spectroscopy with
the Bethe-Salpeter Equation
A. Krassnigg1 and M. Blank1
1
Institut f. Physik, University of Graz, Universitätsplatz 5, A 8010 Graz, Austria,
[email protected]
The Bethe-Salpeter equation is used embedded in the Dyson-Schwinger equations
of quantum chromodynamics to construct an as-complete-as-possible
phenomenology of meson spectra. This includes both light quarks and related
phenomena such as the effects of dynamical chiral symmetry breaking, as well as
heavy quarks and the study of quarkonia in the same framework [1]. The goal is to
connect these realms and to identify interesting states in each case, thus laying the
fundament for meson (and also baryon) studies beyond spectroscopy.
References
[1]
Krassnigg, A., “Survey of J=0,1 mesons in a Bethe-Salpeter approach”,
Phys. Rev. D80, 114010 (2009)
67
From (In)Homogeneous Bethe-Salpeter Amplitudes to Observables
M. Blank1, V. Mader1 and A. Krassnigg1
1
Institut f. Physik, University of Graz, Universitätsplatz 5, 8010 Graz
[email protected]
We investigate properties of light mesons in a Dyson-Schwinger - Bethe-Salpeter
approach. In particular, decay constants, hadronic decays, and electromagnetic
properties are considered from a phenomenological perspective in the wellestablished rainbow-ladder truncation. New possible grounds for applications of
such investigations are opened via improved calculational and numerical
techniques.
All Stationary Axi-Symmetric Solutions to Topologically
Massive Gravity
S. Ertl1, D. Grumiller2 and N. Johansson3
1,2,3
Institute for Theoretical Physics, Vienna University of Technology,
Wiedner Hauptstr. 8-10/136, Vienna, A-1040
1
[email protected]
2
[email protected]
3
[email protected]
A brief overview of 3 dimensional gravity and in particular topologically massive
gravity (TMG) will be given, followed by the construction of its stationary axisymmetric version. With this reduced theory all solutions to TMG can be classified
into 4 different sectors: Einstein, Schrödinger, warped and generic. The solutions to
the first three sectors can be constructed explicitly whereas the generic sector
needs numerical examination. Some examples of solutions will be shown including
solitons that asymptote to warped AdS.
References
[1]
Ertl, Grumiller, Johansson, “All stationary axi-symmetric local solution of
topologically massive gravity”, submitted to Class.Quant.Grav
68
Canonical Structure of New Massive Gravity
M. Blagojevi1 and B. Cvetkovi1,2
1
Institute of physics, P.O. Box 57, 11001 Belgrade, Serbia
Institute for Theoretical Physics, Vienna University of Technology,
Wiedner Hauptstr. 8-10/136, Vienna, A-1040, Austria
Email: [email protected], [email protected]
2
We construct the first-order Lagrangian for new massive gravity (NMG) [1] and use
the covariant expression for the conserved charges proposed by Nester [2] to
calculate the energy and angular momentum of the maximally symmetric solution.
We use the full power of Dirac's method for constrained Hamiltonian systems to
show that the dimension of the physical phase space is four per spacetime point,
which corresponds to two Lagrangian degree of freedom [3].
The analysis of the AdS asymptotic region confirms that the asymptotic symmetry is
described by two independent Virasoro algebras with classical central charges.
References
[1]
Bergshoeff E, Holm O. and Townsend P., “Massive gravity in three
dimensions”, Phys.Rev.Lett. 102: 201301 (2009)
[2]
Nester J. M. , ”A covariant Hamiltonian for gravity theories”, Mod. Phys. Lett.
A 6 2655(1991)
[3]
Blagojevi M. And Cvetkovi B., in preparation.
Emergent Geometry and Gravity from Yang-Mills Matrix Models
H. Steinacker
Universität Wien, Physik
Matrix Models of Yang-Mills type provide a remarkable pre-geometric approach to
geometry and gravity. Space-time is described as a non-commutative brane
solution of the model, i.e. as sub-manifold of R^D. Gauge fields, scalar fields and
matter arise on the brane as fluctuations of the matrices around such a background,
and couple to aneffective metric interpreted in terms of gravity. We show how
curvature and physically relevant geometries can be realized in this framework.
Several types of geometries are identified, in particular "harmonic"and "Einstein"
type of solutions. The relation to non-commutative gauge theory and the role of
UV/IR mixing is explained. The IKKT model with D=10 and close relatives are
69
singled out as promising candidates for a quantum theory of fundamental
interactions including gravity.
Towards a Description of Physics beyond the Standard Model
with On-Shell Effective Theories
W. Waltenberger
HEPHY, ÖAW, Vienna
Nikolsdorfergasse 18, A 1040 Wien, Austria
[email protected]
With the LHC providing the first inverse nanobarns of proton-proton collision data, a
new era of particle physics has started.
While most efforts currently concentrate on measurements of standard model
physics in this new energy range, the Vienna group also prepares for its search for
physics beyond the standard model, with a strong focus on supersymmetric models.
Historically, search strategies have been developed around the minimal
supergravity (MSUGRA) and the gauge-mediated symmetry breaking (GMSB)
models. Recently a new, generic tool has been developed: MARMOSET (mass and
rate modeling in on-shell effective theories).
It is an event generator that revolves around the construction of simplified on-shell
effective Lagrangian terms, which are designed to model LHC data effectively, i.e.
without reference to an underlying fundamental theory. These effective Lagrangians
put strong constraints on the candidates for a new fundamental theory.
In this talk, the idea of on-shell effective theories will be presented, and its
implications for physics analysis at the LHC will be discussed.
M. Benedikt
CERN, CH-1211 Geneva 23, [email protected]
MedAustron is a planned centre for hadron therapy and diagnosis in Austria. The
centre is based on a synchrotron which will deliver beams of protons up to 800
MeV/c and carbon ions up to 400 MeV/c per nucleon with intensities of 1010
protons/s and 4.108 ions/s, respectively. Although the accelerator layout is primarily
dedicated to clinical application, dedicated beam time for research applications in
70
the domain of medical radiation physics, radiation biology and experimental physics
is also foreseen.
Layout requirements for the medical and research applications are established. Civil
engineering design is conducted in Austria, where the accelerator complex is
designed in collaboration with CERN. A mandatory Environmental Impact
Assessment (Umweltvertraeglichkeitspruefung) is currently for review with the
Austrian Authorities. Following the EIA approval expected at the end 2010, groundbreaking is scheduled for early 2011. First beams for application are scheduled for
2014.
This presentation will summarize the up-to-date layout of the MedAustron facility,
status of the project and outlook on usability for the different applications with
emphasize on research activities for experimental physics.
The Physics Cluster for Atomic and Subatomic Physics
H. Abele (Univ. of Technology, Vienna), C.W. Fabjan (ÖAW and Univ. of
Technology, Vienna), J. Schmiedmayer (Univ. of Technology, Vienna),
E. Widmann (ÖAW)
It is planned to bring together the Institute of High Energy Physics (HEPHY) and
the Stefan- Meyer Institute (SMI), forming a new Institute of Particle Physics which
will be in close scientific, technological and geographic location to the ‘Atominstitut’
(ATI) of the Univ. of Technology, Vienna . Together, these institutes would form the
Physics Cluster for Atomic and Subatomic Physics. At the Physics Cluster we will
develop a unique research programme comprising a threefold approach to
fundamental problems in particle physics: (1) accelerator-based high-energy
physics for direct discoveries, (2) precision studies of the strong interaction
searching for new exotic hadronic excitations (3) ultra high precision experiments at
low energies with discovery potential not accessible with the conventional methods
of particle physics.
In the coming decade research will focus on exploiting the discovery potential at
accelerators, LHC and KEK, with emphasis on Physics beyond the Standard Model
and on studies of exotic nuclear matter at Frascati, at J-PARC and FAIR. The new
research line of ultra high precision experiments will start from present expertise
with precision experiments with cold and ultracold neutrons at the ILL or at FRMII,
atoms, molecules or nuclear transition. It will focus on observables, which are
sensitive to physics beyond the Standard Model, such as the breaking of
fundamental symmetries (e.g. C, P and T), the variability of fundamental constants,
aspects of gravity and ultra weak interactions or Supersymmetry. We will describe
the research aims and the potential this Cluster for Atomic and Subatomic Physics
will bring to particle physics.
71
FAKT-22 Audi Max: Fr, 10 Sept. 2010, 9:00 Uhr
The FOPI Experiment at GSI-SIS
O. N. Hartmann1, P. Bühler1, K. Suzuki1, and J. Zmeskal1
1
Stefan-Meyer-Institut für Subatomare Physik (SMI)
der Österreichischen Akademie der Wissenschaften,
Boltzmanngasse 3, 1090 Wien
The FOPI experiment [1] at the Schwerionensynchrotron SIS of the GSI
Helmholtzzentrum [2] for heavy ion research, located at Darmstadt, Germany, is a
detector for charged particles emerging from nuclear reactions, induced by heavy
ions or hadrons on a fixed target. It provides nearly full coverage of the solid angle.
Already since 1990 the FOPI detector is being operated at the GSI, in subsequent
construction phases, where the newest one is a time of flight detector based on
timing RPC's installed in 2007. Heavy ion collisions in the energy range from 90
AMeV to 2 AGeV have been studied as well as proton and pion induced reactions.
The presentation will contain an overview of the FOPI physics program – the
nuclear equation of state, stopping and transparency in heavy ion collisions, inmedium effects of hadrons in the light and the strange quark sector including the
search for bound states involving strange mesons. Available results will be
discussed and an outlook on future activities will be given.
The SMI has joined the FOPI collaboration more recently and contributed special
hardware parts for the elementary reactions, which will be briefly discussed as well.
References
[1]
http://www-fopi.gsi.de
[2]
http://www.gsi.de
Rabi Spectroscopy and Excitation in a Gravity Cavity
of Neutron Matter Waves
T. Jenke1, P. Geltenbort2, H. Lemmel1 and H. Abele1
1
Atominstitut TU Wien, Stadionallee 2, 1020 Vienna, Austria
Institut Laue-Langevin, 6 rue Jules Horowitz, 38042 Grenoble Cedex 9, France
2
Gravity experiments might provide an answer for the “big questions” about space,
time, and a unification of all forces, where - as most physicists believe - space-time
is not restricted to four dimensions. Hypothetical extra-dimensions, curled up to
cylinders or tori with a small compactification radius should lead to deviations from
Newton’s gravitational law at very small distances1. These ideas triggered gravity
72
experiments of different kinds, which in the past ten years have validated Newton’s
gravitational law down to about 50 μm.
The basic problem in searching for new physics at small distances is that the size of
the objects under study must be reduced, too, going along with a reduction of signal
intensity. At the same time, the electrostatic background increases. Our way out is
the interaction of a macroscopic system, here a mirror for neutron reflection, with a
pure quantum mechanical system, i.e. the excitation of bound quantum states of a
neutron in the gravity potential of the earth. We demonstrate that the method of
Rabi spectroscopy2 usually used in atom optics can now be applied to quantum
states in the gravity potential of the earth3-5 together with a mechanical or magnetic
coupling. This technique allows a precise measurement of quantum mechanical
phase shifts of a Schrödinger wave packet bouncing off a hard surface in the
gravitational field of the earth. The idea behind this method is that phase shifts in
gravity potentials can be related to frequency measurements with unprecedented
accuracy. These spectroscopy experiments on gravitation within the qBounce6
measurements are a starting point for experiments linked to string theories with
large volume compactifications1 and/or cosmology because Newtonian gravity and
hypothetical fifth forces evolve with different phase information and limits on a
hypothetical strength can be derived.
References
1.
Arkani-Hamed, N., Dimopolos, S. & Dvali, G. Phenomenology, astrophysics
and cosmology of theories with submillimeter dimensions and TeV scale
quantum gravity. Phys. Rev. D59, 086004 (1999).
2.
Rabi I. I. et. al., The molecular beam resonance method for measuring
nuclear magnetic moments. The magnetic moments of 3Li6, 3Li7 and 9F19.
Phys. Rev. 55, 526 (1939).
3.
Nesvizhevsky, V. V. et. al., Quantum states of neutrons in the Earth’s
gravitational field. Nature 415, 299 (2002).
4.
Nesvizhevsky, V. V. et. al., Study of neutron quantum states in the gravity
field. Eur. Phys. J. C40, 479 (2005).
5.
Westphal, A. et. al., A quantum mechanical description of the experiment on
the observation of gravitationally bound states. Eur. Phys. J. C51, 367
(2007).
6.
Abele, H. et. al., QuBounce: The dynamics of ultra-cold neutrons falling in
the gravity potential of the Earth. Nucl. Phys. A827, 593c (2009).
We gratefully acknowledge support from the Austrian Science Fund (FWF) under
Contract No. I529-N20 and the German Research Foundation (DFG) within the
Priority Programme (SPP) 1491 “Precision experiments in particle and astrophysics
with cold and ultracold neutrons“, the DFG Excellence Initiative “Origin of the
Universe”, and DFG support under Contract No. Ab128/2-1.
73
Standard Model Tests with PERC
X. Wang, PERC Collaboration
Atominstitut, TUW, Stadionallee 2, 1020 Wien, Österreich,
[email protected]
We address a number of questions which are at the forefront of particle physics,
with main emphasis on the search for new physics beyond the Standard Model of
particles physics, and in particular, on the question of unification of all forces shortly
after the Big Bang. This grand unification is not part of the Standard Model, and
new symmetry concepts are needed like left-right symmetry, fundamental fermion
compositeness, new particles, leptoquarks, supersymmetry, and many more.[1]
We present a case study on a new type of cold neutron beam station PERC, for the
investigation of various observables in free neutron's b-decay. With PERC, we will
be able to obtain a beam of decay electrons and protons under well-defined and
precisely variable conditions from the cold neutron beam [2]. Therefore the spectra
and angular distributions of the emerging decay particles will be distortion-free on
the level of 10-4, more than 10 times better than achieved today.
PERC is part of a priority program SPP 1491 "Precision experiments in particle and
astrophysics with cold and ultra-cold neutron"(FWF, Contract No. I 534-N20)
References
[1] H. Abele, "The neutron. Its properties and basic interactions" Prog. Part. Nucl.
Phys., 60, 1 (2008).
[2] D. Dubbers at al. "A clean, bright, and versatile source of neutron decay
products", Nucl. Instrum. Meth. A 596, 238 (2008),
Status and Plans of experiment E17 at J-PARC
B. K. Wünschek1
On behalf of the E17 J-PARC collaboration
Stefan-Meyer-Institute for subatomic physics, Boltzmanngasse 3, 1090 Wien,
[email protected]
Kaonic helium is an advantageous exotic atom to measure KN interaction at
threshold energy. Especially X-ray spectroscopy is useful in order to investigate the
shift and width of the energy levels, evoked due to strong interaction between
nucleus and Kaon.
74
The 2p level shift was determined in kaonic 4He by the KEK-PS E570 experiment in
2007 [1]. The obtained shift of 2 ± 2(stat) ± 2(sys) eV solved the long-standing
so-called kaonic helium puzzle: most of the theoretical predictions with optical
models estimated a very small shift of 0eV, whereas all previous experiments
(1971-1983), obtained a large shift of around -40eV. Although E570 experiment
restricted a large shift for kaonic 4He, the case for 3He is not solved yet.
Furthermore, crucial information on the isospin dependence of the KN interaction in
kaonic helium can be obtained by measuring X-ray transitions in kaonic 3He. In
E17, the X-ray transition 3p2d in liquid kaonic 3He will be measured with high
precision at the K1.8BR beam line at J-PARC [2], which is one of the first
experiments at J-PARC. To achieve the desired precision of <2eV the principle of
the successful setup for E570 will be used, among others the reutilization of Silicon
Drift Detectors (SDD). Those Detectors are characterized by their good energy
resolution (140 eV at 5.9 keV) and time resolution (< 1s), as well as their
thickness of around 500m which makes these detectors extremely sensitive for
low-energy X-rays at high rates.The detectors will be mounted around the liquid 3He
target, inside the chamber. Both in Vienna and at KEK in Japan, altogether ten
devices were adjusted and subjected to systematic tests in order to optimize them
for the experiment. The testing procedure and the arrangement of the devices will
be discussed in detail.
References
[1]
S. Okada, et al., Phys. Lett. B 653 (2007) 387.
[2]
R.S. Hayano, Proceedings of EXA08/LEAP08, Eds. B. Juhasz, J. Marton,
E. Widmann and J. Zmeskal, Hyperfine Interactions.
New Measurement of the 62Ni(n,J) Cross-Section with n_TOF
at CERN Relevant for the Astrophysical S-Process
C. Lederer1, E. Berthoumieux2,3, M. Calviani3, D. Cano-Ott4, N. Colonna5,
I. Dillmann6, C. Domingo-Pardo7, G. Giubrone8, C. Guerrero3,4, F. Gunsing2,
M. Heil7, E. Jericha10, F. Käppeler9, H. Leeb10, C. Massimi11, A. Mengoni12,
A. Pavlik1, J.L Tain8 V. Vlachoudis3, A. Wallner1, Christina Weiß10 and
the n_TOF Collaboration
1
Faculty of Physics, University of Vienna, Vienna, Austria;
CEA/Saclay - DSM, Gif-sur-Yvette, France;
3
CERN, Geneva, Switzerland;
4
CIEMAT, Madrid, Spain;
5
INFN, Bari, Italy;
6
Faculty of Physics, Technical University Munich, Garching, Germany;
7
GSI, Darmstadt, Germany;
8
Instituto de Fisica Corpuscular, CSIC-Universidad de Valencia, Valencia, Spain;
9
Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany;
2
75
10
Atomic Institute, Technical University of Vienna, Vienna, Austria;
INFN, Bologna, Italy;
12
IAEA - Nuclear Data Section, Vienna, Austria;
11
Neutron capture reactions play a dominant role for building up heavy elements in
stellar nucleosynthesis (slow s-process and rapid r-process). The abundance
pattern of these elements, specifically their s-process contribution is strongly
correlated to neutron capture cross-sections. At present, neutron capture crosssections for elements of mass numbers 60<A<120 suffer from large uncertainties.
The latter directly affect the interpretation of r-process model calculations, because
r-process abundances are determined by subtracting the s-process contribution
from the solar abundance.
In 2009, a campaign to measure all stable Ni and Fe isotopes - the seed nuclei of
the astrophysical s-process, at the neutron time-of flight facility n_TOF at CERN has
started. At n_TOF, neutrons are produced by spallation reactions of pulsed 20
GeV/c protons on a Pb target. The flight path of approx. 185 m guarantees a high
energy resolution. The capture yield over an energy range from1 eV to 1 MeV is
measured by detecting the prompt gamma-de-excitation of the compound nucleus
with a pair of liquid scintillation detectors featuring low neutron sensitivity. Last year,
56
62
data taking of the reactions Fe(n,J) and Ni(n,J) has been successfully finished
and the analysis is ongoing. First results will be presented.
Developments towards Radiocarbon Dating
of Ultra-Small Dna Samples
K. Mair, J. Liebl , P. Steier , W. Kutschera
Vienna Environmental Research Accelerator (VERA) Laboratory,Fakultät für Physik
– Isotopenforschung, Universität Wien, Währingerstrasse 17, A-1090 Wien, Austria
Radiocarbon (14C) dating using Accelerator Mass Spectrometry (AMS) is a well
established method. Standard methods of AMS typically require a sample size
of about one milligram carbon, which, however, is not available in our recent
efforts towards dating DNA from small human brain tissue samples using the
14
C bomb peak [1]. We are presently developing methods to reliably measure
samples in the range of ~10 Pg C. In decreasing the sample size, the main
challenge is the control of the laboratory background which typically stays
constant, and finally dominates the measurement result. In order to keep carbon
contamination at the lowest possible level, an argon atmosphere – instead of air
- was provided in sample handling, sample preparation, and ion source loading.
Most of these tasks were performed in an argon glove box.
Since we couldn’t find a significant difference in the carbon background for the
ultra-small samples between sample preparation in laboratory air and argon
atmosphere, we tested our argon-controlled set-up with mg-size samples of
76
geological graphite (nominally zero 14C content), and found a radiocarbon age
of 77 000 years BP. This is the lowest 14C background we have measured at
VERA so far. It corresponds to a fraction modern carbon (F14C) value of (6.3 ±
1.4)x10-5. This is about one 14C half life "older" than samples processed in
laboratory atmosphere. However, It was not possible to measure such a low
value with ~10 μg graphitized carbon samples, because contamination from
other sources seems to dominate the overall background.
In a different investigation, we studied the mass of carbon contamination
incorporated during different steps of sample preparation using small samples
highly enriched in 13C. The amount of contamination with normal carbon (99%
12
C) present in CO2 from sample combustion can be assessed by measuring
13
CO2/12CO2 ratios using an RGA (residual gas analyzer). Additional
contamination from the graphitization process was determined by measuring
13
C/12C ratios with AMS. An overall amount of 0.12 to 0.15 Pg C contamination
was found in this way [2].
References
[1]
Spalding, K. L., Bhardwaj, R. D., Buchholz, B. A., Druid, H., Frisen, J.,
“Retrospective birth dating of cells in humans”, Cell 122, 133-143 (2005).
[2]
Liebl, J., Avalos Ortiz, R., Golser, R., Handle, F., Kutschera, W., Steier. P.,
Wild, E. M., “Studies on the preparation of small 14C samples with an RGA
and 13C enriched material”, accepted for publication in Radiocarbon.
Recent Advances in AMS of 36Cl with a 3-MV-Tandem
M. Martschini1,*, O. Forstner1, R. Golser1, W. Kutschera1, S. Pavetich1,
A. Priller1, P. Steier1, M. Suter2 and A. Wallner1
1
VERA Laboratory, Fakultät für Physik - Isotopenforschung, Universität Wien,
Währingerstraße 17, A-1090 Wien, Austria; *[email protected]
2
Ion Beam Physics, Department of Physics, ETH Zürich, Schafmattstraße 20,
CH-8093 Zürich, Switzerland
36
Cl (t1/2 = 0.30 Ma) is widely used for exposure dating of carbonate rocks such as
limestone and calcite. Accelerator mass spectrometry (AMS) with its high sensitivity
36
36
-13
allows to measure Cl at natural isotopic concentrations ( Cl/Cl ~ 10 ) but
requires high particle energies for the separation from the stable isobar 36S. At
VERA (Vienna Environmental Research Accelerator) we had performed the first
36
Cl exposure dating measurement with a 3-MV tandem accelerator, operating our
machine at 3.5 MV, using foil stripping and a split-anode ionization chamber [1].
36
We evaluated the performance of various detectors for Cl [2]. With the ionization
chamber and a residual energy signal from a silicon strip detector, we now achieved
an equally good 36S suppression at 3 MV terminal voltage compared to 3.5 MV in
our previous measurements. To further increase the 36S suppression we
77
investigated energy loss straggling in various counting gases and the effect of
“energy focusing” [3] below the maximum of the Bragg curve. Comparison of
experimental data with simulations and published data [3,4] yielded interesting
insight into the physics underlying the detectors. Energy loss, energy straggling and
36
angular scattering determine the S suppression.
In addition, we improved ion source conditions, target backing materials and the
cathode design with respect to sulfur output and cross contamination. These
changes allow higher currents during measurement (35Cl current | 5 PA) and also
increased the reproducibility. We achieve an injector to detector efficiency for 36Cl
ions of 8% (16% stripping yield for the 7+ charge state in the accelerator, 50% 36Cl
detection efficiency), which compares favorable to other facilities. We will
demonstrate that 36Cl measurements, which are competitive to larger tandems, are
now possible.
References
[1]
P. Steier, O. Forstner, R. Golser, W. Kutschera, M. Martschini, S. Merchel,
T. Orlowski, A. Priller, C. Vockenhuber, A. Wallner, Nucl. Instr. Methods
Phys. Res. B 268 (2010) 744
[2]
T. Orlowski, O. Forstner, R. Golser, W. Kutschera, M. Martschini, S.
Merchel, A. Priller, P. Steier, C. Vockenhuber, A. Wallner, Nucl. Instr.
Methods Phys. Res. B 268 (2010) 847
[3]
H. Schmidt-Böcking, H. Hornung, Z. Physik A286 (1978) 253
[4]
L.C. Northcliffe, R.F. Schilling, Nucl. Data Tabl. A7 (1970) 233
A New Cryogenic Target and Microwave Cavity for Hyperfinestructure
Spectroscopy of Antiprotonic Helium
O. Massiczek1, S. Friedreich2, B. Juhász2, E. Widmann2 and J. Zmeskal2
1
Stefan-Meyer Insitiute for subatomic Physics, Austrian Academy of Sciences,
Boltzmanngase 3, 1090 Wien, [email protected]
2
Stefan-Meyer Insitiute for subatomic Physics, Austrian Academy of Sciences,
Boltzmanngase 3, 1090 Wien
A new cryostat with pulse tube refrigeration and gas-tight microwave cavity with a
laser and antiproton window has been designed and built to study the hyperfine
structure of antiprotonic Helium-3 and Helium-4. The improvements between this
and the old system [1] will be explained. Also the performance of the setup during
the 2009 and 2010 beamtimes at the CERN Antiproton Decelerator will be
discussed.
References
[1]
J. Sakaguchi, H. Gilg, R.S. Hayano, T. Ishikawa, K. Suzuki, E. Widmann,
H. Yamaguchi, F. Caspers, J. Eades, M. Hori, D. Barna, D. Horvath, B.
78
Juhasz, H.A. Torii, T. Yamazaki
“Cryogenic tunable microwave cavity at 13 GHz for hyperfine spectroscopy
of antiprotonic helium“
Nucl. Instrum. Methods in Phys. Research A 533, 598 (2004).
Hyperfine Structure Spectroscopy with Antiprotonic Helium
S. Friedreich1, B. Juhász2, O. Massiczek2 and E. Widmann2
1
Stefan-Meyer Institute for subatomic Physics, Austrian Academy of Sciences,
Boltzmanngasse 3, 1090 Wien, [email protected]
2
Stefan-Meyer Institute for subatomic Physics, Austrian Academy of Sciences,
Antiprotonic helium is a neutral exotic atom, consisting of a helium nucleus, an
electron and an antiproton. The interactions of the angular momenta and spins
of its constituents cause splitting within the principle states. The measured
transition frequencies between hyperfine levels can be compared with threebody QED calculations as a test of the theory.
Previous measurements have been performed on antiprotonic 4He [1], [2].
Currently a similar transition state is being measured in 3He. Due to the
additional coupling of the antiproton orbital angular momentum to the hellion
spin, it consists of an octuplet of hyperfine substates instead of a quadruplet.
A measurement of this system would lead to a more stringent test of the theory
and also address systematic errors therein.
A completely new setup has been designed and built for the hyperfine structure
measurements of antiprotonic 3He. It will be reported on the test of the new
microwave cavities and the first spectroscopy results.
References
[1]
E. Widmann, J. Eades, T. Ishikawa, J. Sakaguchi, T. Tasaki, H. Yamaguchi,
R.S. Hayano, M. Hori, H.A. Torii, B. Juhász, D. Horváth, Yamazaki,
“Hyperfine structure of antiprotonic helium revealed by a laser-microwavelaser resonance method”, Phys. Rev. Lett. 89, 243402, (2002)
[2]
T. Pask, D. Barna, A. Dax, R.S. Hayano, M. Hori, D. Horváth, S. Friedreich,
B. Juhász, O. Massiczek, N. Ono, A. Sótér, E. Widmann, “Antiproton
magnetic moment determined from the HFS of antiprotonic helium”, Phys.
Lett. B, 678 (1,6), 55-59 (2009)
[3]
V.I. Korobov, Z.-X. Zhong, “Precision spectroscopy of antiprotonic helium”,
Phys. Rev. A, 80, 042506, (2009)
79
AMS Measurement of the Reaction 35Cl(n,J)36Cl and its
Relevance to Astrophysics and Nuclear Technology
S. Pavetich1, T. Belgya2, M. Bichler3, I. Dillmann4, O. Forstner1, R. Golser1,
4
2
1
1
1
3
F. Käppeler , Z. Kis , M. Martschini , A. Priller , P. Steier , G. Steinhauser ,
2
1
L. Szentmiklosi and A. Wallner
1
VERA Laboratory, Faculty of Physics, University of Vienna, Währinger Str. 17,
1090 Vienna, Austria, [email protected]
2
Department of Nuclear Research, Institute of Isotopes, Hungarian Academy of
Sciences, 1525 Budapest, Hungary
3
Atominstitut der Österreichischen Universitäten (ATI), Stadionallee 2, 1020
Vienna, Austria
4
Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe,
Germany
36
Cl is a long-lived radionuclide (t1/2 = 301000 a), which is dominantly produced via
the reaction 35Cl(n,J)36Cl. The seed nuclei of this reaction, the stable 35Cl, acts as a
neutron poison in the nucleosynthesis processes during later burning phases of
stars. This makes the reaction important for astrophysical calculations, aiming to
reproduce the abundances of elements. Due to the long half-life of 36Cl, the cross
section and the production rate of the above reaction are also important for nuclear
technology and nuclear waste management.
The two main goals of this work are: (i) the production of an independent 36Cl/35Cl
standard for accelerator mass spectrometry (AMS); and (ii) the determination of the
Maxwellian averaged cross section (MACS) of 35Cl(n,J)36Cl at 25 keV using AMS.
Approaching the first goal, NaCl pellets were irradiated at the TRIGA Mark II reactor
at the ATI in Vienna and at the Budapest research reactor. The neutron flux was
monitored via the reference cross section of 197Au(n,J)198Au (gold foils attached to
and gold powder homogenously mixed into the pellets) and determined by activity
measurements on the foils and the pellets. With this data we calculated a 36Cl/35Cl
ratio for the irradiated samples.
The AMS measurements on these samples were performed at VERA (Vienna
Environmental Research Accelerator), relative to a standard from ETH Zurich. The
36
35
comparison of the Cl/ Cl ratio calculated from the activity measurements and
measured ratios by AMS shows a systematic discrepancy of 5%.
To determine the neutron capture cross section of 35Cl, AMS measurements were
performed on two samples, which were irradiated with neutrons of a MaxwellBoltzmann energy distribution of 25 keV at the Forschungszentrum Karlsruhe. A
preliminary mean value for the cross section is deduced by combining the AMS
data and the neutron-fluence. The relevant cross section for nucleosynthesis in
stars (MACS) will be calculated by weighting the mean value for the cross section
with a Maxwell-Boltzmann energy distribution of 25 keV.
The irradiation techniques and the measuring procedure by AMS will be discussed
and our new results will be compared with previous measurements of neutron
35
capture on Cl.
80
HFOLD a Program Package for Calculating MSSM Two-Body Higgs
Decays at Full one-Loop Level
W. Frisch1 and H. Eberl2
1
Hephy Vienna, [email protected]
Hephy Vienna, [email protected]
2
HFOLD (Higgs Full One-Loop Decays) is the first public available program which
calculates all MSSM Higgs two-body decays at full one-loop level. The
renormalization is done in the DRbar scheme following the SPA convention. The
program is easy to use and supports Les Houches in- and output format. We
compare the numerical results from HFOLD with some other public available
programs. Particular attention is paid to the size of the electroweak corrections.
Using Vienna Tier-2 Grid computing for data analysis of the CMS
experiment and for other research projects
N. Hörmann1, D. Liko2 and G. Walzel3
1
Institute of High Energy Physics (HEPHY), Nikolsdorfergasse 18, 1050 Wien,
Austria, [email protected]
2,3
Institute of High Energy Physics (HEPHY), Nikolsdorfergasse 18, 1050 Wien,
Austria
In February this year the LHC accelerator at CERN has reached the new center of
mass energy of 7 TeV. This will allow particle physicists to complete the current
understanding of the Standard Model and to search for new physics like the Higgs
boson or supersymmetric particles. The collected huge amount of data from the
LHC experiments is being eagerly analyzed by thousands of physicists around the
world. Supported by the European Union and other funding agencies, a worldwide
computing infrastructure, the Grid, has been established to provide the required
resources in terms of computing power and storage capacity. To support the
Austrian scientific community, the Austrian Academy of Sciences and the
University of Innsbruck, have established a large Tier-2 computing center. Data
from the CMS experiment are continuously being transferred to the Institute of High
Energy Physics in Vienna and then analyzed by the local analysis team, which has
already provided first physics results. This presentation will review the workflow of
the data analysis at the Vienna computing center and give a brief overview of the
ongoing studies of the first CMS data. Finally we show how researchers from other
fields like radiobiology and theoretical physics are using these powerful computing
resources.
81
Jeremy – A Code for Radiological Characterization of Accelerator
Components at CERN
R. Fröschl
CERN DGS RP, CH-1211 Geneve 23, Switzerland, [email protected]
Beam losses are responsible for material activation in components of the CERN
accelerator complex. The prediction of the radionuclide inventory of these
components represents a crucial task for various reasons. On the one hand, it is
important to know the activation levels in order to classify the material as
radioactive and devise appropriate handling procedures with respect to
maintenance. On the other hand, a detailed radionuclide inventory is also
necessary for the elimination of radioactive waste to the final repositories.
A specifically-written code, JEREMY, calculates the radionuclide inventory
analytically by using the so-called Matrix Method. The calculations involve the use
of cross-sections, representative spectra and radiological history. Calculations with
JEREMY are virtually instantaneous and can be repeated over a set of input
parameters for sensitivity studies. The design and the current status of the code will
be presented as well as the planned experimental validation and the first
applications.
References
[1]
Magistris, M., “The matrix method for radiological characterization of
radioactive waste”, Nucl. Instr. and Meth. Phys. Res. B 262 (2), 182-188
(2007)
GENEUS - A Program Designed for Nuclear Data Evaluations
D. Neudecker1, S. Gundacker2, T. Srdinko2, V. Wildpaner2 and H.Leeb2
1
Inst. of Atomic and Subatomic Phys., TU Wien, Wiedner Hauptstr. 8, 1040 Wien,
[email protected]
2
Inst. of Atomic and Subatomic Phys., TU Wien, Wiedner Hauptstr. 8, 1040 Wien
Nuclear data evaluations merge experimental and theoretical knowledge in order to
produce evaluated information which is suitable for the design of novel nuclear
technologies and radioactive waste incineration- e.g. accelerator driven system,
82
generation IV reactors, fusion reactors. However, for these applications uncertainty
information is of utmost importance, especially for energy ranges with scarce
experimental information (beyond 20 MeV).
GENEUS (General Nuclear Data Evaluation and Uncertainty System) is a program
package which evaluates angle-integrated cross sections for neutron-induced
reactions and associated covariance matrices [1]. The program starts out from
model cross sections provided by the nuclear model code TALYS-1.0[2] and prior
covariance matrices containing parameter uncertainties and model defects. The
former account for the limited knowledge of the parameters of the nuclear model
employed and the latter for deficiencies of the model with regard to actually
measured values. In few update steps, experimental information, consisting of cross
sections as well as covariance matrices is added via the linearized Bayesian
Update. The output is given in the ENDF-format, the standard format for nuclear
data libraries. The method is illustrated by means of evaluations on Pb-208 and Mn55.
Work partly supported by the EURATOM project IP_EUROTRANS and the F4Eproject NUDATA_FILES. The views and opinions expressed herein do not reflect
necessarily those of the European Commission.
References
[1]
Leeb H., Neudecker D. and Srdinko Th., ”Consistent Procedure for Nuclear
Data Evaluation Based on Modeling”, Nucl. Data Sheets 109 2762 (2008)
[2]
Koning A. J., Hilaire S. and Duijvestijn M. C., “TALYS-1.0”, Proc. of the
Internat. Conf. on Nucl. Data for Sci. and Tech.: ND2007, Nice, France, April
22-27, 2007, EDP Sciences, 211 (2008)
Silicon Photomultiplier for Subatomic Physics Experiments
- Performance Studies at SMI
G.S.M. Ahmed1,2, P. Bühler1, J. Marton1 and K. Suzuki1
1
Stefan Meyer Institute, Austrian Academy of Sciences, Vienna, Austria
[email protected]
2
Al-Azhar University, Faculty of Science, Physics Department, Cairo, Egypt
1
The detection of a low-intensity light photon flux is one of the key processes in
experimental physics, from solid-state physics to high-energy physics and
astroparticle physics. The energy of the particles to be observed by detectors is
partly converted into visible photons which then are detected by appropriate
sensors.
Silicon Photomultipliers (SiPMs) are semiconductor devices consisting of many
photon microcounters positioned on a common Silicon substrate. Each single
microcounter (avalanche photo diode, APD) is working in the Geiger-mode. SiPMs
83
have numerous advantages compared to other photodetectors (fast response, high
gain, photon counting capability, compactness, insensitivity to magnetic fields, low
voltage operation) and represent a promising solution for the light detection and
providing the potential to replace classical photomultipliers (PMT) in many
applications, such as scintillating fiber readout, imaging Cherenkov counter [3-4].
In our institute we are characterizing SiPMs from different manufacturers, in order to
find out the optimum conditions for a given application. Measurements of dark
current, dark count rate and cross-talk of this device have been presented
elsewhere [1-2].
One of the most important features of SiPMs is the capability of ultrafast timing
(picoseconds range). Here we are presenting our latest results of the SiPMs timing
performance at SMI. Furthermore, main SiPMs features and two examples of
applications are described.
Acknowledgements
This work is partly supported by INTAS (project 05-1000008-8114) and
Hadronphysics2 (project 227431). One of us (G.A.) acknowledges the support by
the Egyptian Ministry of higher education.
References
[1] G.S.M. Ahmed., “Studies of GM-APD (SiPM) Properties”, Journal of
Instrumentation 4, (P09004), (2009)
[2] D. Renker., “Geiger-mode avalanche photodiodes, history, properties and
problems”, Nuclear Instruments and Methods in Physics Research A 567,
(48–56) (2006)
[3] G.S.M. Ahmed., “Study of timing performance of Silicon Photomultiplier and
application for a Cherenkov detector”, Nuclear Instruments and Methods in
Physics Research A (in press), arXiv:1004.4144
[4] K. Suzuki., “Development of SciFi/CheFi detector with SiPM readout”, Nuclear
Instruments and Methods in Physics Research A 620, (75-77) (2009)
Belle II Silicon Vertex Detector: Mechanics and Cooling
I. Gfall1, T. Bergauer1, M. Friedl1, C. Irmler1, M. Valentan1
1
Institute of High Energy Physics, Nikolsdorfergasse 18, A-1050 Vienna, Austria
[email protected]
The Belle experiment at KEK in Tsukuba, Japan is the only operating B-factory
today and its precision measurements have led to the justification of the Nobel Prize
earned by Kobayashi and Maskawa in 2008. In June 2010, the machine was
brought to a halt for a promising future, namely an upgrade to be completed until
2014. By this time all important components are to be exchanged for an
84
unprecedented performance boost of the accelerator (KEKB) and the Belle
Detector. With this upgrade, KEKB will beat its own luminosity world record (2.11 x
1034 cm-2s-1) by a factor of 40 [1].
The Belle Detector consists of several sub detectors. One of those detectors is the
Silicon Vertex Detector (SVD). The SVD is located close to the beam pipe to allow
high precision track finding. The proximity to the beam pipe and the high beam
currents result in a very high level of background radiation for the SVD. To cope
with the new challenges of higher backgrounds and the need for even higher
precision measurements, the Origami sensor design was developed. This design
comes with a great performance increase that is fit to cope with the new Belle II
requirements.
Nevertheless it is important to implement a light and yet stable mechanical
construction that can withstand the radiation and temperature conditions such that
the detectors capabilities are not compromised. In order to push the performance
further, a cutting edge cooling system is under development to further improve the
signal to noise ratio. This cooling system will operate with CO2 to allow highly
efficient electronics cooling with a minimal cooling tube thickness to avoid additional
material inside the acceptance region.
References
[1]
M. Friedl,”Upgrade of the Belle Silicon Vertex Detector”, 1st international
conference on Technology and Instrumentation in Particle Physics
proceedings, article in press in NIM A
Ground Motion Mitigation in the Main Linac of CLIC
J. Pfingstner1, D. Schulte2 and M. Hofbaur3
1
PhD student at Graz University of Technology working at CERN,
[email protected]
2
European Organization for Nuclear Research (CERN)
3
Private University UMIT Hall/Tyrol, Austria
The future linear collider CLIC (Compact Linear Collider) is CERN’s propose for a
successor of the LHC (Large Hadron Collider). The design of CLIC requires ultralow particle beam emittances, which makes the accelerator very sensitive to ground
motion. Without countermeasure, the beam quality would be already unacceptable
after a few seconds.
In our work we present a feedback algorithm, which mitigates the parasitic effects of
ground motion in the main linac of CLIC efficiently. We use an adaptive controller,
which is composed of two parts: a system identification unit and a SVD control
algorithm. The system identification unit calculates on-line estimates of the timechanging accelerator behaviour. This precise model, which can adapt to system
changes, is used by the control algorithm. If the system identification unit would not
85
be used, drifting accelerator parameter would cause a mismatch between the real
accelerator behaviour and the model used by the controller, which would result in a
poor controller performance.
Standard system identification algorithms cannot be used in an accelerator
environment. The indispensable system excitation cause a not tolerable emittance
growth, if it is applied thoughtless. Instead a special excitation scheme consisting of
interleaved beam bumps was implemented, which keeps the emittance growth at an
acceptable level. However, this special excitation has the disadvantage that not the
complete system can be identified anymore. To still get an all over model of the
system, we use the identification data and interpolate them with the help of a beam
oscillation amplitude model, derived for the main linac of CLIC.
The control algorithm uses the identified system data, which are the orbit response
matrix R. With the help of the SVD decomposition of R, a very efficient filter can be
created. This filter reconstructs the ground motion components, which are causing
the majority of the emittance growth. At the same time the filter strongly suppresses
the measurement noise of the sensors.
The described adaptive control algorithm was simulated with the help of the particle
tracking code PLACET. The system identification algorithm is capable of identifying
system changes in a step- and drift-like manner. A learning coefficient can be used
to balance between noise suppression and adaption speed. In a typical
configuration, 4.1 sec. are needed to recover from 90% of a step-like model
change. The steady-state error is about 13%. This error comes from measurement
noise and the limited accuracy of the amplitude model. The SVD controller
succeeds in keeping the emittance growth at a level of about 0.1 nm rad. It also
keeps the pulse-to-pulse jitter at a very low level, by efficiently suppressing
measurement noise.
Concluding, we would like to point out that the presented adaptive control scheme
is capable of suppressing the ground motion effects in the main linac of CLIC
efficiently. Additional advantages of the scheme are reduction of down-time to
measure R in a traditional way and the possibility of carry out system diagnostics
and error detection.
References
Sery, A. and Napoly, O., “Influence of ground motion on the time evolution of beams
in linear colliders”, Phys. Rev. E 53, 5323-5346 (1996).
Steinhagen, R. J., “LHC Beam Stability and Feedback Control”, PhD thesis,
Technische Hochschule Aachen (2007)
86
GEM Detector Development for Hadron-Physics Experiments
P. Müllner1,a, und J. Zmeskal1
1
Stefan Meyer Institut für subatomare Physik
a
[email protected]
The next experiments in hadron-physics aim at studying rare processes with
improved sensitivity (e.g. PANDA) [1]. The technical requirements for these
experiments include fast detectors for charged particles with large acceptance and
excellent tracking capabilities. With the GEM (Gas Electron Multiplier) technology it
is possible to build detectors, which meet the demands for such experiments.
The GEM technology bases on a thin polymide foil with a copper cladding on both
sides [2]. A large number of microholes are chemically etched into this foil. By
applying a voltage difference of several hundred volts, an electrical field of several
kV/cm is produced inside the holes. Therefore the holes acts as a multiplication
channel for electrons and as a trap for positive charged particles. A GEM detector is
a gas detector with one or more GEM foils mounted between the cathode and
anode.
The SMI (Stefan Meyer Institute for subatomic physics) in Vienna build a triple GEM
detector with an active area of 50x50 mm2, which was tested with PIXE (Proton
Induced X-ray Emission) at the VERA (Vienna Environmental Research
Accelerator). The location dependence of the intrinsic efficiency across the
detection area was examined. Due to the collected experience from the results of
these test, the SMI build now a new triple GEM detector prototype with a larger
active area of 100x100 mm2 and improved readout electronics.
References
[1]
Schmitt, L., “The PANDA detector at FAIR”, Nuclear Instruments and
Methods in Physics Research A 581, 542-544 (2007)
[2]
Sauli, F., “GEM: A new concept for electron amplification in gas detectors”,
Nuclear Instruments and Methods in Physics Research A 386, 531-534
(1997)
87
8.5 FKP / NESY – Festkörperphysik / Physik an Neutronenund Synchrotronstrahlungsquellen
Fachausschuss Festkörperphysik –
Scientific Committee Solid State Physics (FKP)
Fachausschuss Forschung mit Neutronen und Synchrotronstrahlung
Scientific Committee Research with Neutrons and Synchrotron
Radiation (NESY)
Parallel Session FKP - NESY
Zeit
Time
Vortragender
Lecturer
Vortragstitel
Title of Lecture
9:00 – 9:40
Keynote:
Christian Pfleiderer
(TU München)
Versatile neutron scattering techniques
with ultra-high resolution
9:40 – 9:55
Michael Benedikt
(CERN)
Status of the MedAustron project
9:55 – 10:10
Heinz Amenitsch
(ÖAW)
Real time SAXS analysis on nanosystems
10:10 – 10:25
Maxim Erko
(MU Leoben)
Water freezing in nanopores
10:25 – 10:40
Michael Leitner
(Univ. Wien)
Studying atomic diffusion by coherent
synchrotron radiation
11:40 – 11:55
Benedetta Marmiroli
(ÖAW)
Sub 100 μs studies of fast chemical and
biological reactions using a free-jet
micromixer
11:00 - 11:30
88
Fachausschuss Festkörperphysik - Scientific Committee
Solid State Physics (FKP)
Scientific Committee Research with Neutrons and Synchrotron
Radiation (NESY)
Zeit
Time
Vortragender
Lecturer
Vortragstitel
Title of Lecture
13:30 – 14:00
Keynote:
Heinz Krenn
(Univ. Graz)
How to stabilize the magnetism
of ultrasmall nanomagnets ?
14:00 – 14:15
Rainer T. Lechner
(MU Leoben)
Magnetic properties of epitaxial GeMnTe
determined by crystal structure
14:15 – 14:30
Andreas
Buchsbaum
(TU Wien)
Magnetic Properties of Co Clusters on Alumina
on Ni3Al(111)
14:30 – 14:45
Kashif Nadeem
(Univ. Graz)
Magnetic studies of fine maghemite
nanoparticles prepared by microwave plasma
synthesis
14:45 – 15:10
Gang Chen
(Univ. Linz)
Damascene process for controlled positioning
of magnetic colloidal nanocrystals
15:10 – 15:30
Matthias
Wegscheider
(Univ. Linz)
Ferromagnetic resonance studies on epitaxial
Fe and Fe3Si films on GaAs (001)
15:30 - 15:50
15:50 - 16:20
Thomas Pichler
(Univ. Wien)
Tailoring carbon nanostructures:
Unravelling the electronic properties of
low-dimensional quantum solids
89
16:20 - 16:35
David Geist
(Univ. Wien)
Nanocrystallization by heating of amorphous
Zr3Al made by repeated cold rolling
16:35 - 16:50
Florian Libisch
(TU Wien)
AT&S Prize Lecture:
Simulation of coherent, large-scale
nanostructures
16:50 - 17:05
Armin Moser
(TU Graz)
Organic dielectrics influence the
crystallographic structure of pentacene thin
films
17:05 - 17:20
Daniel
Primetzhofer
Anton Paar Prize Lecture:
Electronic Interactions of Slow Ions
17:20 - 17:35
Christoph
Uiberacker
(MU Leoben)
Current conservation in nonequilibrium
networks
17:35 - 18:00
Fachausschusses FKP
FKP Annual General Assembly
17:35 - 18:00
Fachausschusses NESY
NESY Annual General Assembly
90
Freitag - Friday 10 September 2010 / HS 403
Fachausschuss Festkörperphysik - Scientific Committee
Solid State Physics (FKP)
Scientific Committee Research with Neutrons and
Synchrotron Radiation (NESY)
Zeit
Time
Vortragender
Lecturer
Vortragstitel
Title of Lecture
9:15 - 9:45
Keynote:
Aaron M. Andrews
(TU Wien)
InGaAs/GaAsSb/InP Material System for
MIR and THz Quantum Cascade Lasers
9:45 - 10:00
Hermann Detz
(TU Wien)
Ring cavity induced performance
enhancement in mid-infrared and terahertz
quantum cascade lasers
10:00 - 10:15
Bernhard Mandl
(Univ. Linz)
Au – free growth of InAs nanowires
10:15 - 10:30
Thomas Moldaschl
(TU Wien)
Two-photon excitation of InAs / GaAs
quantum dots
10:30 - 10:45
Moritz Brehm
(Univ. Linz)
Giant Ge surface diffusion length and stable
island sizes during Stranski-Krastanow
nucleation of SiGe/Si(001) islands
10:45 - 11:00
Rainer T. Lechner
(MU Leoben)
X-ray scattering studies of magnetic
CoFeO nano-cubes
91
FKP-NESY-1: Grüner Hörsaal, Do, 9 Sept, 09:00 Uhr
Versatile Neutron Scattering Techniques with Ultra-high Resolution
C. Pfleiderer
Physik-Department, Technische Universität München, D-85748 Garching, Germany
Neutron scattering has a long history as a unique experimental tool in the
exploration of condensed matter systems. The development of neutron resonance
spin flippers, invented over twenty years ago in Munich, has recently paved the way
to a new generation of versatile neutron scattering techniques with ultra-high
resolution. Following a basic introduction I will illustrate the opportunities for the
scientific community referring to examples in the field of emergent phenomena. This
includes the search for genuine non-Fermi liquid phases, the identification of
enigmatic forms of hidden order and, last but not least, the origin of unconventional
superconductivity.
M. Benedikt
CERN, CH-1211 Geneva 23,
[email protected]
MedAustron is a planned centre for hadron therapy and diagnosis in Austria. The
centre is based on a synchrotron which will deliver beams of protons up to 800
MeV/c and carbon ions up to 400 MeV/c per nucleon with intensities of 1010
protons/s and 4.108 ions/s, respectively. Although the accelerator layout is primarily
dedicated to clinical application, dedicated beam time for research applications in
the domain of medical radiation physics, radiation biology and experimental physics
is also foreseen.
Layout requirements for the medical and research applications are established. Civil
engineering design is conducted in Austria, where the accelerator complex is
designed in collaboration with CERN. A mandatory Environmental Impact
Assessment (Umweltverträglichkeitsprüfung) is currently for review with the
Austrian Authorities. Following the EIA approval expected at the end 2010, groundbreaking is scheduled for early 2011. First beams for application are scheduled for
2014.
This presentation will summarize the up-to-date layout of the MedAustron facility,
status of the project and outlook on usability for the different applications with
emphasize on research activities for experimental physics.
92
Real Time SAXS Analysis on Nanosystems
H. Amenitsch1, B. Marmiroli1, B. Sartori1, F. Cacho-Nerin1, K. Jungnikl1,
and M. Rappolt1
1
Institute of Biophysics and Nanosystems Research, Austrian Academy of
Sciences, Schmiedlstr. 6, A-8042 Graz, Austria,
Small Angle X-ray Scattering (SAXS) has developed as a powerful working horse in
almost all synchrotrons in the world. Its fundamental strength is the capability of in
situ investigations for all states of matter - gas, liquid and solid – as well as probing
materials in bulk, surface sensitive (grazing incidence SAXS) or with high local
spatial resolution (scanning SAXS).
This presentation should summarize the current state of the art investigating
self-assembly processes i.e. watching molecules in situ to form nano(bio)materials
or the in situ response of supramolecular structures to physical/chemical parameter
changes as temperature, stretch etc. Some highlights of the current research
covering the fields of life sciences till nanomaterials will be discussed and will
include the above mentioned application areas of the SAXS and GISAXS
technique. The examples will range - to name just a few – from self-assembly of
nanotubes in form of helical ribbons [1], in situ study of the formation of mesoporous
materials on surfaces as well as in solution [2], to self-assembly of nanoparticles
[3,4].
At the same time, for advanced studies on nanomaterials, the integration of in
situ chemical and physical perturbation technicques into the experimental set-up is
a prerequisite. Some sophisticated instrumental developments like ultrafast mixers
with μs-resolution [5,6], in situ aerosol reactors [7], or optical tweezers [8] are
presented with adequate examples.
References
[1]
C.V. Teixeira, et al., “Formfactor of a N-layered helical tape and its
application to nanotubeformation of Hexa-peri-hexabenzocoronene based
molecules “, J. Appl. Cryst (2010) in press.
[2]
D. Grosso, et al., “Periodically ordered nanoscale islands and mesoporous
films composed of nanocrystalline multimetallic oxides”, Nature Materials 3
(2004) 787.
[3]
R. Viswanatha, et al., “Growth mechanism of cadmium sulfide
nanocrystals ”J. Phys. Chem. Let. 1 (2010) 308.
[4]
F.Toma, et al., “Efficient water oxidation at carbon nanotube–
polyoxometallate electrocatalytic interfaces“, Nature Chemistry, (2010), in
press.
[5]
B. Marmiroli, et al., “Free jet micromixer to study fast chemical reactions by
small angle X-ray scattering”, Lab on Chip. 9 (2009) 2063.
[6]
W. Schmidt, et al., ”Accessing Ultrashort Reaction Times in Particle
Formation with SAXS Experiments: ZnS Precipitation on the Microsecond
93
[7]
[8]
Time Scale”, JACS (2010) 10.1021/ja101519z.
I. Shyjumon, et al., “Novel in situ setup to study the formation of
nanoparticles in the gas phase by small angle x-ray scattering”, Rev. Sci.
Instr. 79, (2008) 43905.
D.Cojoc, et al., ”Scanning x-ray microdiffraction of optically manipulated
liposomes”, APL 91, (2008) 234107.
Water Freezing in Nanopores
M. Erko1, D. Wallacher2, A. Höll3 and O. Paris4
1
Institute of Physics, University of Leoben, 8700 Leoben, Austria.
[email protected]
2
Helmholtz Zentrum Berlin für Materialien und Energie, 14109 Berlin, Germany.
3
Helmholtz Zentrum Berlin für Materialien und Energie, 14109 Berlin, Germany.
4
Institute of Physics, University of Leoben, 8700 Leoben, Austria.
The structure and dynamics of supercooled liquid water and of amorphous ice is a
very active area of current research [1, 2]. Confinement induces new phenomena
such as melting point suppression, and in some cases, water seems even not to
freeze at all, as shown in recent differential scanning calorimetry (DSC)
measurements [3]. Micelle-templated porous silica materials, such as SBA-15 and
MCM-41 [4] represent ideal model systems for studying water in nano-confinement.
The pores of these materials are perfectly ordered on a two-dimensional hexagonal
lattice with lattice parameter of a few Nanometers, making these materials ideal for
investigations with small-angle X-ray (SAXS) and neutron (SANS) scattering
methods [5, 6]. We performed Synchrotron-SAXS and SANS measurement on
water-filled MCM-41 and SBA-15 porous materials with pore diameters ranging
from 2 nm – 9 nm. The advantages of the two complementary scattering
techniques, SAXS and SANS are ideally applied to our system. The high brilliance
synchrotron radiation makes strain effects in the order of 10^-3 resolvable. The
phase contrast variation in neutron scattering allows a detailed investigation of
density change of water by using a proper H2O/D2O.
Two phenomena could be observed during freezing and melting of confined water.
First, the water density change during phase transformation results in change of the
scattering contrast and therefore changes the scattering intensity. Second, the
strain-induced contraction and expansion of the pore lattice during water phase
transformation leads to a shift of the Bragg-Peak position [7]. Both effects are
observed for water in large pores exactly at the phase transition temperatures
predicted by DSC. Moreover, these effects are present even for water confined in
pores below 2,5 nm where water is assumed not to freeze. Additionally, we
performed cooling and heating cycles on samples with different pore filling fractions.
Different number of the few water layers on pore walls show different freezing and
94
melting behaviour which is discussed together with the results from fully-filled pores
with different diameters.
References
[1]
O. Mishima, H. E. Stanley, Nature 396, 329-335 (1998).
[2]
P. G. Debenedetti, H. E. Stanley, Physics Today 56, 40-46 (2003).
[3]
G. H. Findenegg, S. Jähnert, D. Akcakayiran, A. Schreiber, ChemPhysChem
9, 2651-2659 (2008).
[4]
D. Zhao, J. Feng, Q. Huo, N. Melosh, G.H. Fredrickson, B.F.
Chmelka, G.D. Stucky, Science 279, 548-52 (1998).
[5]
M. Erko, D. Wallacher, A. Brandt, O. Paris, Journal of Applied
Chrystallography 43, 1-7 (2010).
[6]
G.H. Findenegg, S. Jahnert, D. Müter, J. Prass, O. Paris, Phys. Chem.
Chem. Phys. 12, 7211-7220 (2010).
[7]
J. Prass, D. Mueter, P. Fratzl, O. Paris, Applied Physics Letters 95, 083121
(2009).
Studying Atomic Diffusion by Coherent Synchrotron Radiation
M. Leitner1, B. Sepiol, F. Gröstlinger, and G. Vogl
Fakultät für Physik, Universität Wien, Strudlhofgasse 4, 1090 Wien
The static structure of solids on the atomic scale is nowadays very well known.
Knowledge about dynamics, i.e. how this structure evolves via jumps of the atoms,
is much scarcer, however, and is only rarely based on direct experimental
investigations.
X-ray Photon Correlation Spectroscopy (XPCS) is an upcoming method for studying
the dynamics of matter on small scales. It consists in scattering coherent radiation
at the sample and analyzing the temporal fluctuations of the scattered intensity.
Recently we have succeeded in applying this method for the first time to dynamics
on the atomic scale [1]. I will present our results on diffusion in the system Cu-Au,
specifically the influence of short-range order on the atomic jumps. I will also give
preliminary results on the dynamics in a metallic glass and in B2-ordered NiAl.
References
[1]
M. Leitner, B. Sepiol, L.-M. Stadler, B. Pfau, and G. Vogl, “Atomic diffusion
studied with coherent X-rays” Nature Mat. 8, 717 (2009).
95
Sub 100 μS Studies oF Fast Chemical and Biological Reactions Using
a Free- Jet Micromixer
B. Marmiroli1, F. Cacho-Nerin1, B. Sartori1, G. Grenci2, J. Perez3, P. Laggner1
and H. Amenitsch1
1
Institute for Biophysics and Nanosystem Research, Austrian Academy of Sciences,
Schmiedlstrasse 6, Graz, 8042, Austria
2
IOM - CNR, SS 14 km 163.5, 34012 Basovizza (TS), Italy
3
SWING beamline - Synchrotron SOLEIL,
L'Orme des Merisiers BP 48 Saint-Aubin, Gif sur Yvette, 91192, France
Short time-scales are fundamental for gaining insight in fast chemical and biological
reactions like the nucleation and growth of nanoparticles or the conformational
changes of proteins. In the present communication we describe first the design, the
fabrication process, and the system engineering of a microfluidic mixer aimed to
studies of fast chemical and biological reactions with a time resolution lower than
100 μs [1]. The mixer is based on hydrodynamic focusing. It works in the laminar
regime, and mixing occurs only by diffusion that can be predicted and controlled.
The mixing is completed inside the device before the nozzle, and a free liquid jet in
air exits from the device. The time evolution of the reaction is separated spatially in
the steady state flow along the liquid jet exiting from the device. Measuring the
signal form the jet at different distances from the nozzle exit corresponds to
measuring the reaction at different times from the beginning of the mixing. The
geometry and dimensions of the device have been optimized by Finite Element
Analysis, and are stringent: outlet channel 500 μm long and 10 μm wide, and exit
nozzle 8 μm wide in order to produce a stable jet. The channels depth is 60 μm.
Even if the device has been optimized for synchrotron SAXS measurements [2], the
choice of a free jet as observation region overcomes the problem of the material
selection for the microfluidic chamber. This enables to use the same device with
different investigation techniques (i.e Light Scattering and Raman Spectroscopy).
The device usually works with a total flow rate of 300 μl/min, leading to a jet speed
of 13 m/s, and to a mixing time of 45 μs. Anyway it can bear flow rates larger than 1
ml/min, corresponding to a nominal time resolution of 26ns/μm. The micromixer
can be used to study a wide variety of fast chemical and biological reactions by
adequately tuning the operating conditions. The maximum pressure inside the
device is less than the denaturation limit for proteins. The shear rate is not sufficient
to destabilize a typical small protein of ~100 amino acids in water, but it could have
influence on bigger proteins or when using viscous solvents. Therefore, the
possibility to use the device with biological reagents must be evaluated for each
specific case. Latest results of SAXS characterization of the jet itself, and of the
early stages of nucleation and growth of nanoparticles will be presented.
References
[1]
Marmiroli, B. et al., “Free jet micromixer to study fast chemical reactions by
small angle X-ray scattering”, Lab on Chip 9, 2063-2069 (2009)
96
[2]
Marmiroli, B. et al., “Experimental set-up for time resolved small angle X-ray
scattering studies of nanoparticles formation using a free -jet micromixer “,
Nuclear Instruments and Methods in Physics Research B 268, 329-333
(2010)
How to Stabilize the Magnetism of Ultrasmall Nanomagnets?
H. Krenn and K. Nadeem
Institut für Physik
Karl-Franzens-Universität Graz, Universitätsplatz 5, A-8010 Graz, Austria
Magnetic nanoparticles play an outstanding role in advanced high-density magnetic
data storage, in magnetic fluids, in paleo- and rock-magnetism and as amplifiers for
magnetic resonance imaging. As the sizes of monodomain particles are smaller
than few nanometers the so-called superparamagnetic limit is reached - a critical
threshold - beyond which a stable magnetic state cannot be maintained. Thermal
agitation erases the stored magnetism due to large fluctuations. Thus the question
how to overrule such a limitation is of fundamental interest not only for increasing
the bit density of storage media, but is also related to the role of magnetic phase
transitions within and around small nanomagnets. The well-known Nèel-Brown
relaxation model of isolated particles is the prominent starting point to study the
enduration of “blocked” magnetized particles. However, magnetic relaxation is not
solely explainable by magnetic blocking mediated by magnetocrystalline and shape
anisotropy as it is manifested by a plenty of recent publications. Disorder and
frustration on the surface of nanoparticles become dominant as the surface to
volume ratio increases, therefore exchange anisotropy, exchange bias, spin-glass
freezing and interparticle interactions must be taken into account. Most of these
phenomena stiffen the magnetic moment orientation of nanomagnets although the
total magnetic moment is partly diminished. Material parameters, the mutual
interactions of the core/shell structure and dipolar coupling between particles
provide a rich field for studying thermal activation, scaling laws and frustration
phenomena of such complex arrangements of nanoparticles (“superspin-glass”).
We investigate powders and mildly compacted samples of ferrite (NiFe2O4,
CoFe2O4, J-Fe2O3) and antiferromagnetic particles (NiO) particles to follow the route
from isolated superparamagnetic particles toward interacting dense nanomagnets.
The aim is a tutorial-like presentation of this challenging new field of reduced
dimensional magnetism with an outlook for future applications in materials science
and data storage.
97
Magnetic Properties of Epitaxial GeMnTe Determined
by Crystal Structure
R.T. Lechner1,2, G. Springholz1, M. Hassan1, H. Groiss1, R. Kirchschlager1,
J. Stangl1, N. Hrauda1, and G. Bauer1
1
Institut für Physik, Montanuniv. Leoben, Franz-Josef-Straße 18, A-8700 Leoben,
Austria
2
Institut für Halbleiter- und Festkörperphysik, Johannes Kepler Universität Linz,
A-4040 Linz
A promising candidate for a ferromagnetic semiconductor (FM) is IV-VI Ge1-xMnxTe
with Curie temperatures as high as 190 K [1] and a solubility limit for Mn of about
90%. The crystalline structure and hence the ferromagnetic properties of MBE
grown samples, however, depend strongly on the Mn concentration as well as on
the growth conditions. The samples were grown by molecular beam epitaxy with
Mn contents ranging from xMn = 0 to 100%. The growth conditions were adjusted to
avoid the formation of prezipitates [2]. The crystal structure of Ge1-xMnxTe changes
as a function of composition due to the fact that pure GeTe is rhombohedrally
distorted, while pure MnTe crystallizes predominantly in the hexagonal NiAs
structure. In the present work, the structure-magnetic properties relationship of Ge1xMnxTe was studied systematically as a function of Mn content by x-ray diffraction
(XRD) demonstrating a switching of the magnetic easy axes from out-of-plane to inplane direction at a certain Mn content measured by SQUID magnetometry. This is
explained by the structural phase transitions occurring in these compound. For xMn
above 50%, however, crystallographic phase separation between antiferromagnetic
MnTe and FM GeMnTe is revealed by synchrotron XRD, resulting in magnetic
exchange coupling effects [3].
References
[1]
Y. Fukuma, H. Asada, S. Miyawaki, T. Koyanagi, S. Senba, K. Goto, and H.
Sato, Carrier-induced ferromagnetism in Ge0.92Mn0.08Te epilayers with a
Curie temperature up to 190 K, Appl. Phys. Lett. 93, 252502 (2008)
[2]
R.T. Lechner, V. Holy, S. Ahlers, A. Navarro-Quezada, D. Bougeard,
J.Stangl, A. Trampert and G. Bauer, Selfassembled Mn5Ge3 nanomagnets
close to the surface and deep inside a Ge1-xMnx epilayer, Appl. Phys.
Lett.95, 023102 (2009)
[3]
R. T. Lechner, G. Springholz, M. Hassan, H. Groiss, R. Kirchschlager,
J. Stangl, N. Hrauda, and G. Bauer, Phase separation and exchange biasing
in the ferromagnetic IV-VI semiconductor Ge1xMnxTe, Appl. Phys. Lett. 97,
023101 (2010)
98
Magnetic Properties of Co Clusters on Alumina on Ni3Al(111)
A. Buchsbaum1, Pardeep K. Thakur2, A. Preobrajenski3, E. Lundgren4,
M. De Santis5, H. C.N. Tolentino5, M. Schmid1 and P. Varga1
1
Institut für angewandte Physik, Technische Universität Wien, Österreich
2
ID08, ESRF, Grenoble, France
3
D1011, MAX-lab, Lund, Sweden
4
Division of Synchrotron Radiation Research, Lund Universitity, Sweden
5
Institut Neel, CNRS & UJF, Grenoble, France
The structure of the 0.5 nm thick oxide film on Ni3Al(111) exhibits holes reaching
down to the metal substrate at the corners of the ( 67 u 67 )R12.2° unit cell. Pd
atoms trapped in these corner holes create metallic nucleation sites where Co
clusters can nucleate and form a well-ordered hexagonal arrangement on the oxide
nanomesh [1]. The crystal structure of these Co clusters has been well
characterized by scanning tunneling microscopy (STM), surface x-ray diffraction
(SXRD) and grazing-incidence small-angle x-ray scattering (GISAXS) [2]. They
show random stacking of closed packed Co planes parallel to the substrate surface.
Magnetic properties of Co clusters with 350 atoms/cluster have been investigated
by x-ray magnetic circular dichroism (XMCD) assisted by STM. This technique
allowed us to measure the orbital and spin contribution to the magnetic moment per
Fe or Co atom, as well as magnetization curves down to temperatures of 7 K and
up to fields of 5 T and correlate the measured magnetic properties to the structure
of the clusters. The Co clusters are super-paramagnetic down to 7K and show bulk
like magnetic moments of 2 PB. From fitting the magnetization curves the
magnetic anisotropy energy (MAE) and the direction of the easy axis can be
determined. The MAE of the Co clusters is enhanced by a factor of 4 compared to
hcp bulk Co and the easy axis is not perpendicular to the surface but tilted. The
magnetization curves also suggest magnetic coupling to the substrate, which
depends on the number of Pd atoms in the corner hole below the clusters.
References
[1]
M. Schmid, G. Kresse, A. Buchsbaum, E. Napetschnig, S. Gritschneder,
M. Reichling, P. Varga, Phys. Rev. Lett. 99, 196104-4 (2007).
[2]
A. Buchsbaum, M. De Santis, H. C.N. Tolentino, M. Schmid, P. Varga,Phys.
Rev. B 81 115420 (2009)
99
Magnetic Studies of Fine Maghemite Nanoparticles Prepared by
Microwave Plasma Synthesis
K. Nadeem1, H. Krenn1, T. Traussing2, R. Würschum2, and D. V. Szabó3
1
Institute of Physics, Karl-Franzens University Graz, Universitätsplatz 5, A-8010
Graz, Austria, e-mail: [email protected]
2
Institute of Materials Physics, University of Technology Graz, A-8010 Graz, Austria
3
Institute for Materials Research III, Karlsruhe Institute for Technology (KIT), 76021
Karlsruhe, Germany
Magnetic properties of maghemite nanoparticles (5nm) (prepared by microwave
plasma synthesis) have been investigated by SQUID-magnetometry. Fine
maghemite nanoparticles consist of magnetically aligned core and of disordered
surface spins [1]. Disordered and frustrated surface spins give pinning effects and
spin-glass freezing at low temperatures [2]. Zero field cooled / field cooled (ZFC/FC)
magnetic measurements show magnetic blocking at 75 K. A model for noninteracting nanoparticles have been simulated to reproduce the experimental
ZFC/FC curves and to calculate effective anisotropy. Effective anisotropy calculated
from the model is larger than the bulk value due to increased surface anisotropy.
Frequency dependent AC susceptibility measurements in the frequency range (0.11000 Hz) have shown an increase of blocking temperature with increasing
frequency. A model of AC susceptibility for non-interacting nanoparticles has been
developed to investigate the shift of blocking temperature within a decade of
frequency. Simulation of the AC susceptibility model produce large shift in blocking
temperature in the frequency range (0.1-1000 Hz). The large value of effective
anisotropy from ZFC/ FC model and discrepancy in the AC susceptibility experiment
and simulation signify the existence of freezing effects at low temperature on the
surface of maghemite nanoparticles. Spin glass freezing on the surface of
nanoparticles is a possible mechanism to overcome the superparamagnetic limit
which commonly erases the magnetic memory of nanomagnets.
References
[1]
[2]
R. H. Kodama and A. E. Berkowitz, “Atomic-scale magnetic modeling of
oxide nanoparticles”, Physical Review B, 59, 6321-6336 (1999)
B.Martinez, X. Obradors, LI. Balcells, A. Rouanet, and C. Monty, “Low
temperature surface spin-glass transition in -Fe2O3 nanoparticles”, Physical
review letters, 80, 181-184 (1998)
The authors thank the Austrian national funds for granting the network projects
(NFN) S10407-N16 and S10405-N16.
100
Damascene Process for Controlled Positioning of
Magnetic Colloidal Nanocrystals
G. Chen,1 M. I. Bodnarchuk, M. V. Kovalenko, G. Springholz, W. Heiss, W. Jantsch
Institute of Semiconductor and Solid State Physics, Linz University,
Altenbergerstr. 69, A-4040 Linz, Austria
Potential applications of nanocrystals have been recently discussed in diverse fields
ranging e.g. from biomedical, plasmonic, photonic, data storage devices, to Lab-ona-chip concepts, nanocrystals. Significant progress has been achieved in the
synthesis of magnetic NCs having well-defined compositions, shapes, structures
and sizes. Meanwhile one major challenging issue remains, namely, to produce
assemblies of colloidal NCs on well-controlled sites, which is essential to enable
separate identification and addressability for single nanoparticle units. In this letter,
we report a straight-forward approach for large scale nano-fabrication with high
accuracy following the same strategy as the well-established Damascene process
in integrated circuit (IC) manufacturing. In the latter, metal interconnects are
produced by depositing a thin Cu film on pre-patterned Si wafers and constriction of
the Cu film to connecting lines is achieved via a chemical-mechanical back
polishing. In our work, the basic idea of this technique is utilized for controlled
positioning of NCs by means of deposition on a pre-patterned template, and
subsequent NC removal by polishing. The present work demonstrates the potential
of such techniques to prepare assemblies of ordered NCs with a size down to 18
nm at low cost and great convenience. Another advantage of this approach is the
absence of suspensions or any other solvent during the final processing step, which
is an advantage in respect to environment-friendly production. This method allows
arranging specific numbers of NCs down to single ones per pit. The structures
produced were characterized by scanning electron microscopy (SEM), atomic forceas well as magnetic force microscopy (AFM; MFM) at room temperature.
Ferromagnetic Resonance Studies on Epitaxial Fe and Fe3Si
Films on GaAs (001)
M. Wegscheider, G. Käferböck, C. Gusenbauer, T. Ashraf, R. Koch
and W. Jantsch
Institute of Semiconductor / Solid State Physics, Johannes Kepler University, Linz,
1
Corresponding Author: email: [email protected]
101
A future spin-based electronics relies on easily implementable semiconductor/ferromagnet junctions. For instance, the realization of a magnetic logic
based on magneto resistive elements [1] or the efficient spin injection into a
semiconductor [2-4] require ferromagnetic heterostructures with a high spin
polarization. Promising candidates are the binary and ternary compounds of the
Heusler alloys [4-5] that exhibit a high spin polarization and are lattice matched to
the semiconductor substrate.
Here we report on ferromagnetic resonance (FMR) results of thin layers of the
Heusler alloy Fe3Si on GaAs(001) and compare them with that of pure Fe films
grown under identical conditions. The films were prepared by standard molecularbeam epitaxy onto in-situ grown GaAs(001) buffer layers terminated by the c(4x4)
superstructure forming the well-defined substrate surface. The growth parameters,
i.e., temperature, thickness and Si content, have been varied in a wide range
accompanied by detailed characterization of the structural and magnetic properties.
FMR is a powerful method to investigate the magnetic anisotropy of ferromagnetic
thin films, in particular to determine the magnetocrystalline anisotropy constants
with high precision. The theoretical evaluation is based on the Landau-LifshitzGilbert equation of motion for the dynamics of FMR. It includes the respective
magnetocrystalline anisotropy energy and thus the anisotropy constants which
define the orientation and hardness of the magnetic axes. They are introduced as
fitting parameters for the calculation of the angular evolution of the magnetic
anisotropy. In addition, the linewidth of the FMR signal provides information on the
relaxation of the magnetization and its interplay with the crystal lattice.
References
[1]
A. Ney, C. Pampuch, R. Koch, and K. H. Ploog, Nature, 425, 485 (2003).
[2]
X. Jiang, R.Wang, S. van Dijken, R. Shelby, R. Macfarlane, G. S. Solomon,
J. Harris, and S. S. P. Parkin, Phys. Rev. Lett. 90, 256603 (2003).
[3]
Y. Ando, K. Hamaya, K. Kasahara, Y. Kishi, K. Ueda, K. Sawano, T. Sadoh,
and M. Miyao, Appl. Phys. Lett. 94, 182105 (2009).
[4]
M. Ramsteiner, O. Brandt, T. Flissikowski, H. T. Grahn, M. Hashimoto,
J. Herfort, and H. Kostial, Phys. Rev. B 78, 121303R (2008).
[4]
J. Herfort, H.-P. Schönherr, K.-J. Friedl and, and K. H. Ploog, J. Vac. Sci.
Technol. B 22, 2073 (2004).
Tailoring Carbon Nanostructures: Unravelling the Electronic
Properties of Low-Dimensional Quantum Solids
T. Pichler
Faculty of Physics, University of Vienna
The presentation will give an overview on our current research focus on the
electronic properties of low dimensional quantum solids. These properties are
102
strongly influenced by basic correlation effects. Archetypical examples of these
systems are fullerenes, graphene, graphite and single wall carbon nanotubes
(SWCNT) which are determined by the local arrangement of their sp2 hybridised
carbon atoms, such that their character is either semi-metallic, insulating,
semiconducting or metallic. Examples of the recent work on how one can analyse
these electronic properties using high energy spectroscopy (electron energy-loss,
photoemission and x-ray absorption spectroscopy) as a probe will be presented.
Special emphasis will be given to the influence of basic correlation effects and local
field corrections on the electronic properties of graphene, graphite and SWCNT.
The latter exhibit for metallic tubes a Luttinger liquid behavior. Special emphasis will
be on the influence of the bundling/ debundling (van der Waals interaction) and the
influence of metallicity selected, i.e. purely metallic vs. purely semiconducting,
SWCNT will be given.
Furthermore, an overview on how to functionalize them in order to tailor their
electronic structure will be given. This includes examples for the three alternative
doping routes, namely, substitution, intercalation and endohedral doping (e.g. by
filling with fullerenes, metals and metallocenes) as well as examples for the growth
of defined innertubes from the different precursors via a thermal nanochemical
reaction. In comparison to graphite intercalation compounds, the electronic
structure of doped graphene will be unravelled. For metallic functionalized
nanotubes doping induced changes will be discussed in the framework of a
dimensionality crossover which causes a change from a one-dimensional metal to a
normal Fermi liquid. The detailed understanding of these fundamental electronic
properties of functionalised fullerenes, graphite, SWCNT and graphene is key to
their future success.
Nanocrystallization by Heating of Amorphous Zr3Al Made by Repeated
Cold Rolling
D. Geist1*, S. II 2, K. Tsuchiya2, G. Stefanov3, H.P. Karnthaler1 and C.
Rentenberger1
1
Physics of Nanostuctured Materials, Faculty of Physics, Univ. of Vienna, 1090
Vienna, Austria
2
Hybrid Materials Center, National Institute for Materials Science, Tsukuba 3050047, Japan
3
Inst. of Metal Science Acad. Angel Balevski, Bulgarian Acad. of Sciences, 1574
Sofia, Bulgaria
*Corresponding author: [email protected]
Nanocrystalline materials (i.e. materials with a grain size < 100 nm) are of strong
scientific interest because of the possible changes of the materials’ properties.
Kilmametov et al. [1] showed that the ion irradiation resistance of the intermetallic
compound NiTi can be enhanced by nanostructuring the material by severe plastic
103
deformation (SPD). Zr3Al is an interesting intermetallic compound in this context
because it was proposed as a nuclear structural material, but showed the drawback
of amorphization upon ion irradiation. Nanostructuring could be a way to bypass this
disadvantage.
Repeated cold rolling and intermediate folding (RCR) is a promising SPD method
because it was shown that the grain sizes that can be achieved are often smaller
than those achieved by any other SPD method [2]. Because of its iterative
character, in principal unlimited amounts of strain can be induced by this method
rendering the samples nanocrystalline or amorphous.
In the present work, coarse crystalline Zr3Al was deformed by RCR. Samples
deformed by up to 80 folding cycles (true strain 80 = 6 600 %) were studied by Xray diffraction (XRD) and transmission electron microscopy (TEM). After 80
foldings, a large volume fraction of the material was amorphous. The mostly
amorphous samples were heated to temperatures up to 973 K in a differential
scanning calorimeter. Using different heating rates, the activation enthalpy of the
recrystallization process and the crystallization enthalpy were determined. TEM and
XRD measurements of the heat-treated samples showed that the initial
nanocrystallization does not result in the equilibrium Zr3Al structure. A metastable
crystal structure forms, which slowly transforms into the equilibrium structure at
higher temperatures.
References
[1]
A.R. Kilmametov, D.V. Gunderov. R.Z. Valiev, A.G. Balogh and H. Hahn,
“Enhanced ion irradiation resistance of bulk nanocrystalline TiNi alloy”,
Scripta Materialia 59 (10), 1027-1030 (2008)
[2]
G. Wilde, “Synthesis of bulk nanocrystalline materials and bulk metallic
glasses by repeated cold rolling and folding (RCR)”, Materials Science
Forum 579, 109-133 (2008)
AT&S Prize Lecture:
Simulation of Coherent, Large-Scale Nanostructures
F. Libisch
Institute for Theoretical Physics, Vienna University of Technology
Nanodevices have become popular systems to investigate a wide variety of
physical effects. The term "nanodevice" in this context refers specifically to the size
that exceeds microscopic dimensions but still lies below the inelastic mean free
path. The dynamics of such devices is governed by a wave equation, the
Schrödinger equation. Applications of the resulting quantum interference effects
include the realization of "qubits" in solid-state devices, high-precision interferencebased metrology, or tunable semiconductor lasers.
104
Current materials for coherent nanodevices include carbon-based thin films, GaAs
heterostructures, superconducting circuits and quantum wells. The length scales
involved range from a few Ångström, the typical size of a defect or adsorption site,
to the linear dimension of the device itself, up to several micrometers and more.
Furthermore, microwave cavities or acoustic resonators of macroscopic dimensions
have been used as experimental "quantum simulators" to measure the dynamics of
wave equations on a simple table-top experiment. To treat this wide range of
different materials and dimensions, we present a flexible, robust and versatile set of
numerical tools to treat eigenstates, time evolution and transport.
We focus in particular on graphene, the first true two-dimensional (2D) solid.
Graphene is attracting considerable attention, mostly due to its unique dynamics of
electrons near the Fermi energy which closely mimics that of a massless Dirac
Hamiltonian. Due to its unique band-structure, quantum interference effects like the
quantum-hall effect have been realized at room temperature. However, lattice
defects, substrate interaction, and chemisorbates destroy the high symmetry of
idealized graphene. Conversely, one could functionalize graphene structures by
specific chemical doping at the edges to tailor device properties. The understanding
of the effect of defects, adsorbates and impurities on device properties is thus key
to the fabrication of graphene-based nanodevices that exploit its unique properties.
Organic Dielectrics Influence the Crystallographic Structure of
Pentacene Thin Films
A. Moser2(a), H.-G. Flesch(a), A. Neuhold(a), M. Edler(b), T. Griesser(b), M. Marchl(a),
A. Golubkov(a), G. Trimmel(c), A. Haase(d), D.-M. Smilgies (e), J. Jakabovi
(f),
(a)
(a)
E. Zojer , and R. Resel
(a)
Institute of Solid State Physics, Graz University of Technology, Austria
Institute of Chemistry of Polymeric Materials, University of Leoben,
Franz-Josef Straße 18, 8700 Leoben
(c)Institute of Chemistry and Technology of Organic Materials, Graz University of
Technology, Stremayrgasse 16, 8010 Graz
(d)
JOANNEUM RESEARCH Forschungsgesellschaft mbH, Institute of
Nanostructured Materials and Photonics, Franz Pichlerstrasse 30 A-8160 Weiz,
Austria
(e)
CHESS Center, Cornell University, 14850 Ithaca, New York, USA
(f)
Department of Microelectronics, Slovak University of Technology, Ilkovi
ova 3,
812 19 Bratislava, Slovakia
(b)
X-ray diffraction as well as atomic force microscopy experiments have been
performed to investigate thin films of pentacene. The films were deposited on
thermally grown SiO2 pre-covered by different organic layers. Modifying substrates
2
[email protected], www.if.tugraz.at
105
in that way is a common method in organic thin-film transistor research. It is known
that the substrate pre-treatments have a strong impact on the performance of the
device as well as on the growth of the active layer. However, there are few reports
about the influence on the crystalline properties of pentacene.
In this work three different systems have been investigated. For one sample series
vacuum deposited polymeric Parylene C - with varying thicknesses - was used as
the dielectric layer. A second series of dielectric layers was prepared by spin
coating a photoreactive polymer (PBHND [poly(bicyclo[2.2.1]hept-5-ene-2,3-(2nitrobenzyl)dicarboxylate)]) onto the wafer. Subsequently the samples were
exposed to UV-light for different time spans. For the third class of systems, a self
assembled film of T-SC/SA [4-(2-(trichlorosilyl)ethyl)benzene-1-sulfonyl chloride (TSC), 30% sulfonic acid T-SA] was used to modify the SiOx surface.
From the obtained x-ray data we find that the investigated pentacene films are
polymorphic and consist of the two commonly observed crystal phases, namely the
thin film phase and the Campbell phase. On weakly interacting substrates, these
phases are typically oriented with their (001) lattice planes parallel to the substrate
surface. Yet in the present investigation it is found that for some dielectric layers the
(001) planes of the thin film phase are tilted approximately 3° and of the Campbell
phase about 10° with respect to the substrate surface. These small deviations in the
structure have a large influence to the in-plane diffraction patterns. Therefore, the
changes in the patterns can be unambiguously attributed to the change of preferred
orientation.
Figure1: Scattering pattern of a pentacene thin film deposited on top of a 5 nm
thick parylene film. The diffraction spots can be indexed with the known thin film
(grey) and Campbell (white) phase by choosing an approximately 3° and 10° tilt of
the 001 direction from the surface normal of the substrate. The radii of the rings
correspond to the structure factor of the diffraction spots.
106
Anton Paar Prize Lecture:
Electronic Interactions of Slow Ions
D. Primetzhofer, S.N. Markin, M. Spitz, and P. Bauer
Institut für Experimentalphysik, Johannes Kepler Universität, Linz, Austria
An investigation of the interaction of slow light ions with solids is of importance for
surface science applications and fundamental understanding of electronic
properties of different classes of materials. Knowledge of charge exchange
processes is urgently required in quantitative surface analysis as applied in Lowenergy ion scattering (LEIS) experiments. These processes are linked to the
electronic structure of the sample. The band structure of solids, in turn, influences
the propagation of ions in matter, i. e. the inelastic energy loss due to electron hole
pair excitation.
Charge exchange processes like neutralization or reionization determine not only
the ion yield in a LEIS experiment and thus its sensitivity, but also the probed
information depth [i]. Recent experiments have shown that the neutralization
behaviour of noble gas ions scattered from single crystal surfaces is far from trivial
and strong crystal effects have to be expected [ii].
Electron hole pair excitation along the trajectory gives rise to deceleration of the
ion via electronic stopping power, S = -dE/dx, which – at least for a free electron
gas – is assumed to be velocity proportional: S = Q·v, as long v << vF, the Fermi
velocity of the sample [iii].
For Cu and Au, a velocity threshold vth is observed for H+ and He+, at vth | 0.18 a.u.,
i.e. a 4·105 m/s. Below vth only sp-electrons can be excited, while the d-electrons
cannot, since the DOS of the d-electrons does not extend up to the Fermi level [iv].
For LiF with a band gap of 14 eV, electron-hole pairs can be excited by ions only if
the velocity is larger than 0.09 a.u [v]. Below, ions are slowed down only by atomic
collisions. This threshold is lower than predicted [vi]. A similar behaviour was found
for other ionic insulators with large band gaps, e.g. KCl.
Comparison of the results for LiF and Cu or Au leads to the question why vth for
insulators is so low. It might be concluded that the effective gap in LiF is a 1 eV, in
contrast to theoretical prediction [vii].
References
[i ]
D. Primetzhofer, M. Spitz, S.N. Markin, and P. Bauer, Phys. Rev B (2009)
[ii]
D. Primetzhofer, S.N. Markin, J.I. Juaristi, E. Taglauer, and P. Bauer, PRL
(2008)
[iii]
P.M. Echenique, F. Flores, and R. H. Ritchie, Solid State Physics (1990)
[iv]
S.N. Markin, D. Primetzhofer, M. Spitz, and P. Bauer, Phys. Rev. B (2009)
[v]
S.N. Markin, D. Primetzhofer, P. Bauer, PRL (2009)
J.M. Pruneda, D. Sánchez-Portal, A. Arnau, J.I. Juaristi, and E. Artacho,
[ vi]
PRL (2007)
[vii]
B. Solleder, L. Wirtz and J. Burgdorfer, Phys. Rev. B (2009)
107
Current Conservation in Nonequilibrium Networks
C. Uiberacker and J. Oswald1
1
Montanuniversität Leoben, Inst. f. Physik; [email protected]
In contrast to the well-known Chalker-Coddington network model [1], which uses
elastic single particle quantum tunneling at saddle points to obtain critical
exponents, the nonequilibrium network model [2-4] describes quantities of
nonquilibrium thermodynamics by using the Landauer-Büttiker approach. In case of
local linear transport at saddles we show that the chemical potential distribution can
be obtained, respecting the boundary condition of injected currents, from an
inhomogeneous system of linear equations. It turns out that the solution is uniquely
determined by the boundary condition, no matter how many current contacts we
have. The seeming contradiction can be resolved by the fact that current is
automatically conserved in the network.
References
[1]
J. T. Chalker and P. D. Coddington, “Percolation, quantum tunnelling and
the integer Hall effect“, J. Phys. C: Solid State Phys. 21, 2665 (1988).
[2]
J. Oswald, “A new model for the transport regime of the integer quantum Hall
effect: The role of bulk transport in the edge channel picture”, Physica E 3,
30 (1998).
[3]
J. Oswald and M. Oswald, “Circuit type simulations of magneto-transport in
the quantum Hall effect regime“, J. Phys.: Condens. Matter 18, R101 (2006).
[4]
C. Uiberacker, C. Stecher, and J. Oswald, “Systematic study of nonideal
contacts in integer quantum Hall systems”, Phys. Rev. B 80, 235331 (2009).
FKP-NESY-19: Grüner Hörsaal, Fr, 10 Sept, 09:15 Uhr
InGaAs/GaAsSb/InP Material System for MIR and THz Quantum
Cascade Lasers
A. M. Andrews1,2, M. Nobile1, C. Deutsch2, P. Klang1, H. Detz1, A. Benz2,
W. Schrenk1, K. Unterrainer2, and G. Strasser1,3
1
Center for Micro- and Nanostructures,
Photonics Institute, Vienna University of Technology, Austria,
Contact: [email protected]
3
University at Buffalo, State University of New York, Buffalo, USA
2
State-of-the-art mid-infrared (MIR) quantum cascade lasers (QCLs) use the
InGaAs/InAlAs/InP material system due to its low effective mass and high
conduction band offset, while the terahertz (THz) and MIR QCLs use the
108
GaAs/AlGaAs material systems due to its tailorable band offset while remaining
lattice matched. Intersubband (ISB) unipolar devices, like QCLs, use bandgap
engineering to control electron energy levels and thus photon wavelengths. In
these material systems the barriers contain aluminum, which provides a high
conduction band offset (CBO) of 0.52 eV for InGaAs/InAlAs and variable CBOs up
to 0.39 eV for GaAs/AlGaAs, but at the cost of a high effective mass in the barrier
layers. The InGaAs/GaAsSb/InP material system [3,4], CBO of 0.36 eV, has the
potential to improve ISB devices by the elimination of aluminum from the barriers,
reducing the effective mass, and Al-oxide from the exposed surfaces, therefore
simplifying subsequent post processing and/or regrowth. The low effective mass for
electrons leads to a spreading of the electron wave function and a higher optical
matrix element and thus improved laser gain. As a consequence of the low effective
mass, the barriers must be thicker, which makes them less sensitive to deviations in
the growth rate caused by cell shutter transients or interface roughness.
We present high power MIR and the first THz QCLs based on
In0.53Ga0.47As/GaAs0.51Sb0.49, Figure 1. The samples discussed here were grown in
a solid-source Riber Compact 32 system with valved crackers for both group V
elements [5]. The valved crackers allow a stable As4 and Sb2 flux, which is required
for reliable lattice-matching. Switching between the materials therefore can be
done by shutter operations. A substrate temperature of 480 °C was used to
minimize the dependence of the GaAsSb composition on substrate temperature.
Growth rates of 1.07 μm/h for InGaAs and 0.52 μm/h for GaAsSb are ensured by Xray diffraction analysis of calibration superlattices. MIR QCLs emitting at 10.7 μm
with 1.2 W optical output powers and a threshold as low as 0.6 kA/cm² were
realized [Nobile et al. submitted APL]. In addition, a 10 μm thick THz QCL
consisting solely of 170 active region periods showed emission around 75 μm with a
threshold current density of 1.7 kA/cm² and operation up to 105K [Deutsch et al.
submitted APL], comparable to published InGaAs/InAlAs THz QCLs.
References
M. Nobile, H. Detz, E. Mujagi, A.M. Andrews, P. Klang, W. Schrenk and
G. Strasser, Appl. Phys. Lett. 95, 041102 (2009)
M. Nobile, P. Klang, E. Mujagi, H. Detz, A.M. Andrews, W. Schrenk and
G. Strasser, Electron. Lett. 45, 1031 (2009)
H. Detz, A.M. Andrews, M. Nobile, P. Klang, E. Mujagi, G. Hesser, W. Schrenk,
F. Schäffler, G. Strasser, J. Vac. Sci. Technol. B 28, C3G19 (2010)
Ring Cavity Induced Performance Enhancement in Mid-Infrared and
Terahertz Quantum Cascade Lasers
H. Detz1, E. Mujagi1, Cl. Schwarzer1, P. Klang1, A. M. Andrews1, 2, W. Schrenk1,
C. Deutsch2, K. Unterrainer2, and G. Strasser1
1
Institute for Solid State Electronics and Center for Micro- and Nanostructures,
109
TU Vienna, 1040 Vienna, Austria,
2
Photonics Institute, TU Vienna, 1040 Vienna, Austria
Quantum cascade lasers (QCLs) are well established as reliable laser sources from
the midinfrared (MIR) to the terahertz (THz) spectral region. These coherent
sources of light are attractive compact emitters for a broad range of applications,
such as free space communications, spectroscopy, imaging and heterodyne
detection. For most of these applications, symmetric far fields and low beam
divergence are of special interest. However, due to small dimensions and elongated
shape of the resonator, the emitted light of standard Fabry-Pérot and surface
emitting QCLs is typically broad and asymmetric. Especially for THz QCLs, the subwavelength dimensions of laser ridge facet lead to inhomogeneous diffractive-like
patterns and limited output intensities.
We describe ring cavity surface emitting lasers (RCSELs) and demonstrate how
MIR and THz emission can effectively be emitted using an advanced ring geometry
[1,2]. Beam narrowing is given by constructive interference of light waves passing
through the slits of a radial, light out-coupling grating on top of the laser. This results
in the realization of single-mode operating ring-cavity QCLs with strongly collimated
symmetric surface emission, with a full width at half maximum of 3° and 15° for MIR
and THz emitters, respectively. For the latter the reduced divergence gives a twofold power enhancement compared to standard edge-emitters. We will present an
extensive study in terms of output power, threshold behavior, beam shaping,
dynamic beam steering and polarization characteristics. Furthermore we will talk
about coherent coupling, two-dimensional integration of ring QCLs and their
applicability in spectroscopy.
References
[1]
E. Mujagi, C. Deutsch, H. Detz, P. Klang, M. Nobile, A. M. Andrews, W.
Schrenk, K. Unterrainer, and G. Strasser, „Vertically emitting terahertz
quantum cascade ring lasers“, Appl. Phys. Lett. 95, 011120 (2009).
[2]
E. Mujagi, M. Nobile, H. Detz, W. Schrenk, J. Chen, C. Gmachl, and G.
Strasser, “Ring cavity induced threshold reduction in single-mode surface
emitting quantum cascade lasers”, Appl. Phys. Lett. 96, 031111 (2010).
Au – Free Growth of InAs Nanowires
B. Mandl
Institute for Semiconductor- and Solid State Physics, University of Linz, Austria
Lattice mismatch and defects at boundaries between different semiconductors are
limiting factors hindering the fabrication of otherwise extremely appealing
heterostructures. It seems that nanowires provide a way to circumvent many of
such problems due to the small contact area between substrate and wire, which
110
apparently can lead to almost defect-free structures even if the interface region itself
may contain some defects. Nanowire growth makes material combinations possible,
which have long been envisioned but are very difficult to realize with conventional
heterostructure growth, like III-V compounds on top of silicon substrates. One such
example is the growth of InAs nanowires, which - like many other nanowire
materials – are usually grown in a vapor-liquid-solid like growth mode with Au seed
particles. InAs is of considerable interest for the electronicdevices due to its low
effective electron mass. However, for the growth on Si, gold is rather unwanted
since it acts as a deep trap in Si, and thus it is crucial to develop other growth
schemes without the need for Au seed particles. We have achieved the controlled
Au-free growth of InAs nanowires on Si, as well as on III-V substrates, using SiOx
or organic layers to "nucleate" wire growth. [1,2] Furthermore position controlled
growth of InAs on Si has also been demonstrated in the literature. [3] However, in
contrast to Au-nucleated nanowire growth, so far only little is known about the
details of this Au-free growth mechanism.
In our work we studied the nucleation and growth mechanism of Au – free
grown InAs nanowires. For the growth of these wires InAs and InP substrates are
covered with a thin layer of SiOx and wires are grown using metal-organic vapor
phase epitaxy (MOCVD). As the possibilities for in-situ observation of growth in
MOCVD are very limited, a series growth studies were carried out. In particular, to
clarify the origin of the Au-free InAs growth on SiOx covered InAs in-situ Low
Energy Electron Microscopy (LEEM) and x-ray photo electron emission microscopy
experiments were carried out. With these in-situ heating experiments it was
determined that In droplets play a crucial role for the wire growth. By comparing the
obtained results with such from commonly used growth mechanisms we determine
the mechanism responsible for our wire growth and develope a corresponding
model.
Finally a comparison of our results to reports of Au free growth in the
literature is made to evaluate how general the derived growth model is.
[1]
[2]
[3]
B. Mandl et al., Nano Lett., 2006, 6 (8), 1817 - 1821
T. Martensson et al., Advanced Materials, 2007, 19 (14), 1801 - 1806
K. Tomioka et al., Nano Lett., 2008, 8 (10), 3475 – 3480
Two - Photon Excitation oF InAs / GaAs Quantum Dots
T. Moldaschl1, W. Parz1, T. Müller1, S. Golka1, G. Strasser2,3 and K. Unterrainer1,3
1
Institut für Photonik, TU Wien, Gußhausstrasse 27-29 / 387, 1040 Wien
[email protected]
2
Institut für Festkörperelektronik, TU Wien, Floragasse 7, 1040 Wien
3
Zentrum für Mikro- und Nanostrukturen, TU Wien, Floragasse 7, 1040 Wien
111
Semiconductor quantum dots (QDs) gained significant impact because of their atom
- like properties. Long coherence times of the excitonic states permit the realization
of quantum optics experiments, so far only possible with single trapped atoms.
Among these realizations are the implementation of quantum logic gates [1] using
single QDs. A key effect for the coherent control, necessary for this implementation,
is the Rabi Oscillation, which has been demonstrated in single- and ensemble QDs
[1-3]. The drawback of this mechanism however, is the need for high excitation
intensities, considering the semiconductor nature of the QDs and their host
material. In this work we show the consequences that arise from using high power
resonant QD excitation.
As a spectroscopic technique we use time resolved spectral hole burning (SHB)
spectroscopy. This differential transmission scheme consists of narrow band ps
pump pulses, generated through spectral shaping of the 80 fs pulses provided by
the Ti:Sapphire Laser system, which are directly used for probing. The sample is a
30 layer InAs QD stack grown on GaAs. In order to be optically accessible by the
laser system, the sample underwent a rapid thermal annealing treatment resulting
in a blue shifted ground state transtion energy of around 1280 meV.
Under low excitation intensities, the excitonic spectral hole |X> as well as the
biexcitonic spectral antihole |XX> is visible if both pump and probe pulses share the
same linear polarization. Once the excitation intensity is increased, there appear
additional spectral holes (|X'> and |XX'>) symmetrically around the resonant |X>
spectral hole. These spectral holes are unambiguously assigned to resonant two photon excitation of the biexciton, proven by polarization and intensity dependent
measurements. The higher energy spectral hole |X'>corresponds to the exciton
state, whereas the lower energy |XX'> is created through stimulated emission from
the biexcitonic cascade |XX'> to |X'>, initiated by probe photons at this respective
energy [4].
The second feature of the SHB spectra is an overall broadening of the absorption
line, which is caused by Coulomb interactions between the resonantly created
excitons in the QDs and carriers that are generated by two - photon absorption in
the surrounding GaAs matrix, which are prone to capture and relaxation processes.
To prove this interpretation the photoluminescence of the sample was recorded only
using pulsed two - photon excitation providing a significant amount of carriers. This
eventually gives rise to an additional source of decoherence for QDs under
resonant excitation [4].
References
[1]
Li, X. et al., “An all optical quantum gate in a semiconductor quantum dot”,
Science 301, 809 (2003)
[2]
Zrenner, A. et al., “Coherent properties of a two – level system based on a
quantum dot photodiode“,
Nature 418, 612 (2003)
[3]
Borri, P. et al., “Rabi oscillations in the excitonic ground state transition of
InGaAs quantum dots“, Phys. Rev. B 66, 081306 (2002)
Moldaschl, T. et al. “Two – photon spectral hole burning spectroscopy of
InAs / GaAs quantum dots“, Appl. Phys. Lett. 97, 1 (2010) (page not
assigned yet)
[4]
112
Giant Ge Surface Diffusion Length And Stable Island Sizes During
Stranski-Krastanow Nucleation of SiGe/Si(001) Islands
M. Brehm*, M. Grydlik, F. Hackl, T. Fromherz, F. Schäffler and G. Bauer
Institute of Semiconductor and Solid State Physics, Johannes Kepler University
A-4040 Linz, Austria
During SiGe island nucleation in the Stranski-Krastanow growth mode, a giant Ge
surface diffusion length is observed across boundaries between substrate areas
with different nucleation states of MBE grown SiGe islands. The different nucleation
states of islands can either be due to a pit-patterned substrate adjacent to a plane
substrate or by covering a part of the substrate with a shutter. In the case of a pitpatterned substrate, the impinging Ge flux is first consumed for the formation of
{105} SiGe facets that decorate the side walls of the pits, while on the planar
substrate regions the Ge coverage is already sufficient for the formation of a wetting
layer (WL) with overcritical thickness on that random island nucleation takes place
along the routes discussed recently [1]. On the pit-patterned field we observe an
exponential decay of the island volumes in the pits with increasing distance from the
border between the patterned and un-patterned regions as well as a zone denuded
from islands on the planar part of the substrate similar to what was reported for linepatterned substrates [2]. We observe distinctly different volume decay constants for
the different morphological evolution stages of the islands that allows us to extract
the Ge capture cross-section of the respective SiGe island shapes (transition
pyramids, pyramids, transition domes, domes, super-domes, as commonly defined
[1]). As far as 50 m from the border of the patterned field islands with a larger
volume as compared to that observed in the center of the patterned area are
observed, indicating that Ge diffuses from the border at least this distance into the
patterned area. This giant diffusion length is also observed in a control experiment,
in that a part of the substrate is shaded off the Ge flux by a shutter. Still, clear
evidence of islands and a Ge wetting layer is observed below the covered area by
atomic force microscopy and spatially resolved photoluminescence (micro-PL)
spectroscopy more than 175 m away from the shutter edge. Surprisingly, for
domes of a critical size a vanishingly small Ge capture cross-section is observed,
where this size depends on the growth temperature. Thus, in our experiments the
domes appear as stable islands with equal volumes on the planar and patterned
part of the substrate within the experimental error. We show that dislocated
2
superdomes form only after each pit on the 200 × 200 m patterned substrate area
is occupied by a fully developed dome. Concomitant with the appearance of
superdomes, the PL of the ordered islands is quenched, indicting that this transition
is triggered by dislocation formation. We demonstrate that, as a consequence of the
large Ge surface diffusivity, the critical coverage, at that the transition between
domes and superdomes occurs, inversely depends on the area of the substrate
pattern unit cell as all Ge deposited within this area diffuses into the pits once a
homogenous dome array is formed over the complete patterned area. Thus, the
combination of spatially resolved growth experiments in combination with micro-PL
113
experiments provides novel insight into the role of surface kinetics during StranskiKrastanow growth on planar and patterned substrates.
[1] M. Brehm et al., Phys. Rev. B 80, 205321 (2009).
[2] G. S. Kar et al., Phys. Rev. Lett. 93, 246103 (2004).
X-Ray Scattering Studies of Magnetic CoFeO Nano-Cubes
R.T. Lechner1, G. Popovski1, W. Heiss2, B. Aichmayer3 and O. Paris1
1
Institut für Physik, Montanuniv. Leoben, 8700 Leoben, Austria;
[email protected]
2
Institut für Halbleiter- und Festkörperphysik, Johannes Kepler Univ. Linz, 8010
Linz, Austria
3
Max-Planck-Institut für Kolloid- und Grenzflächenforschung, 14476 Potsdam,
Germany
We have studied with small and wide angle x-ray scattering (SAXS-WAXS)
techniques magnetic CoFe2O4 core-shell nanocrystals (NC) in solution. The new
type of strongly exchange-coupled iron oxide-based core/shell NC with a cubic
shape (see Fig. 1a) are chemically synthesized and consist according to
transmission electron diffraction (TEM) studies of an antiferromagnetic (AFM) core
of ferrous oxide (wüstite, FexO), which is surrounded by a ferrimagnetic (FiM) shell
of a metal ferrite (CoFe2O4) [1]. These magnetic nanoparticles show not only a
great potential for novel magneto-electronic devices, but also for bio-medical
applications. In this work, we have tried to gain structural information of the core
and shell structure independently. The SAXS-WAXS experiments have been
carried out at the beamline -spot at the synchrotron HZB-BESSYII (Berlin). The
scattering spectra were recorded with a 2D CCD-detector in a setup, which enables
(a)
Fig.1: (a) TEM image of a thin film
(b)
(c)
114
formed by 11-nm cubic FexO/CoFe2O4
NCs. (b) 2D WAXS spectrum of
FexO/CoFe2O4 cubes with nominal 14
nm size measured in a 1wt% solution
sealed in quartz-glass-capillaries with
1.5 mm diameter. (c) SAXS intensity
vs. scattering vector q. From the
comparison
to
the
theoretical
scattering model we derive a size of
~12 nm for the magnetic nano-cubes.
The scattering spectra were recorded
using a x-ray energy of 15 keV at the
beamline P-spot at HZB-BessyII,
Berlin.
the detection of the low (SAXS) and the large q-range (WAXS) from 0.5 nm-1 to 50
nm-1, within one single measurement (see Fig. 1(b)). From the SAXS modulated
intensity distribution over q and the fit with the theoretical scattering curve we can
deduce a cube size of ~11.8 ± 1.4 nm (see Fig. 1(c)). From the position and the
width FWHM of the structural Bragg peaks at large q-values (WAXS) we derive the
size of the wüstite FexO-core of ~9 nm and hence a thickness of the surrounding
CoFe2O3 shell to ~1.5 nm.
Supported by the Austrian Science Fund FWF (P18942) and the European
Community's Seventh Framework Programme (FP7/2007-2013 under n.°226716).
References
[1]
M.I. Bodnarchuk, M.V. Kovalenko, H.Groiss, R.Resel , M. Reissner,
G. Hesser, R.T. Lechner,W.Steiner, F.Schäffler, and W. Heiss, Small 5 (20),
2247-2252 (2009)
115
8.6 GEP – Geschichte der Physik
Montag - Monday 6 September 2010 / Haus der Natur
Fachausschuss Geschichte der Physik –
Scientific Committee History of Physics (GEP)
Parallel Session GEP
Zeit
Time
Vortragender
Lecturer
Vortragstitel
Title of Lecture
15:30 - 15:50
Bruno P. Besser (ÖAW),
Walter M. Iber
Willi Nordberg – ein Physiker
in der Fernerkundung
Harald Markum
(TU Wien)
Der Begriff der Zeit von Aristoteles
bis zur nichtkommutativen Geometrie
16:10 - 16:30
Sonja M. Schreiner
(Univ. Wien)
Die Jesuiten und / oder
wissenschaftlicher Fortschritt: Joseph
du Baudory‘s De novorum systematum
inventoribus quid sentiendum oratio als
(typisches?) Beispiel
16:30 - 16:50
Stanislav Južni
(Univ. of Oklahoma)
Habsburg Enlightenment electricity
and vacuum for far east
15:50 - 16:10
16:50 – 17:10
Franz Pichler
(Univ. Linz)
17:10 - 17:30
Peter Maria Schuster
(EchoPhysics)
116
Robert Adler:
Angewandte Physik im Bereich
der Elektronenröhren
und des Ultraschalls
„Erinnerungen an Professor
Dr. Fritz Kohlrausch“: –
In Memoriam Hofrat
DI Franz Allmer
GEP-1: Haus der Natur, Mo, 6 Sept, 15:30 Uhr
Willi Nordberg – Ein Physiker in der Fernerkundung
B. P. Besser1 und W. M. Iber2
1
Institut für Weltraumforschung, Österreichische Akademie der Wissenschaften,
Schmiedlstraße 6, 8042 Graz
2
Ludwig Boltzmann Institut für Kriegsfolgen-Forschung, Ludwig Boltzmann
Gesellschaft, Schörgelgasse 43, 8010 Graz
Dem (Geo-)physiker Willi Nordberg (1930-1976) und der historischen
Entwicklung der Weltraumforschung und Fernerkundung ist heuer (bis 31.
Oktober 2010) eine Ausstellung im Gerberhaus der südsteirischen
Stadtgemeinde Fehring gewidmet [1].
Willi Nordberg, geboren in Fehring, studierte in den beginnenden
Fünfzigerjahren an der Universität Graz und emigrierte kurz nach seiner
Promotion in die Vereinigten Staaten von Amerika. Dort begann er seine
physikalischen Arbeiten an meteorologischen Problemen im Rahmen des Army
Signal Corps. Mit der Gründung der NASA und des Goddard Space Flight
Centers wechselte er dorthin und war beschäftigte sich mit Fragen der
Satellitenmeteorologie, die in der Projektleitung bei der TIROS-WettersatellitenSerie gipfelte. Mit Ende der sechziger Jahre übernahm er die Leitung des
weltweit ersten nichtmilitärischen Fernerkundungsprogrammes dem später der
Name LANDSAT gegeben wurde. Dabei wurde sowohl das weltraum- als auch
das erdgebundene Forschungssegment erfolgreich aufgebaut.
Nordberg waren nach der erfolgreichen Installation des Satellitensystems nur
mehr wenige Forschungsjahre gegönnt, und so konnte er die vielfältigen
Früchte „seiner Saat“ nicht mehr ernten.
References
[1]
Besser, B.P, W.M. Iber, St. Karner (Hrsg.), “Nordberg – Der Weg in den
Weltraum”, Stadtgemeinde Fehring, Fehring und Graz, 224 S., 2010.
Der Begriff der Zeit von Aristoteles bis zur
nichtkommutativen Geometrie
H. Markum1
Atominstitut, TU Wien
117
Aristoteles definiert die Zeit als abgeleitete Größe aus der Bewegung. In
der klassischen Mechanik geht die Zeit als Parameter in die Newtonschen
Bewegungsgleichungen ein. In der Quantenmechanik sowie in der
Quantenfeldtheorie ist die Zeit ebenfalls ein Parameter in der Schrödinger- oder
Dirac-Gleichung. In der speziellen Relativitätstheorie ergibt sich eine Zeitdilatation
im bewegten Bezugsystem, die Zeit bleibt jedoch ein (relativer) Parameter. Ebenso
in der allgemeinen Relativitätstheorie, wo etwa bei gewissen Metriken Phänomene
auftreten können wie Lösungen in die Vergangenheit. Die fundamentalen
Gleichungen der Physik sind invariant bei Zeitumkehr. Der zweite Hauptsatz der
Thermodynamik verletzt diese Symmetrie und führt zum Auftreten eines Zeitpfeils.
In nichtkommutativen Geometrien wird die Zeit zu einem Operator. Atomuhren
machen die Zeit und die Frequenz zu den mit höchster Präzision messbaren
physikalischen Größen. Ein Überblick über den Begriff Zeit in den verschiedenen
Gebieten der Physik soll gegeben werden.
Die Jesuiten und / oder wissenschaftlicher Fortschritt: Joseph du
Baudory‘s De novorum systematum inventoribus quid sentiendum
oratio als (typisches?) Beispiel
S. M. Schreiner1, F. Römer2 und M. E. Lippitsch3
1
Institut für Klassische Philologie, Mittel- und Neulatein, PhilologischKulturwissenschaftliche Fakultät, Universität Wien, Dr. Karl Lueger Ring 1,
A-1010 Wien, [email protected]
2
Institut für Klassische Philologie, Mittel- und Neulatein, PhilologischKulturwissenschaftliche Fakultät, Universität Wien, Dr. Karl Lueger Ring 1,
A-1010 Wien
3
Institut für Physik, Naturwissenschaftliche Fakultät, Karl-Franzens-Universität
Graz, Universitätsplatz 5, A-8010 Graz
Für den Schul- und Universitätsbetrieb des 18. Jahrhunderts war der Jesuitenorden
von unschätzbarer Bedeutung. Die Societas Jesu spannte ihr wissenschaftliches
Netzwerk über ganz Europa. Geistes- und Naturwissenschaften sind im Barock, in
der Aufklärung und im Rokoko ohne die Jesuiten nicht denkbar. Einer der
Gelehrten, die Theologie und Wissenschaft erfolgreich zu kombinieren verstanden,
war der Franzose Joseph du Baudory (1710-1749), der nicht zuletzt durch sein
entwickeltes rhetorisches Talent große Berühmtheit erlangte. 1762 kam in Paris
eine neue und erweiterte Edition der Oeuvres diverses du Père du Baudory auf den
Buchmarkt. Baudorys Rede „Was man von den Erfindern neuer Systeme zu halten
hat” ist Teil dieser Sammelausgabe. In einer tour d’hôrizon eröffnet Baudory
Einblicke in seine Gedankenwelt und entwickelt seinen ganz persönlichen Zugang
zum wissenschaftlichen Fortschritt, indem er dessen Vor- und Nachteile unter
permanenter Bezugnahme auf zahlreiche prominente Philosophen und
Wissenschaftler erläutert.
118
Habsburg Enlightenment Electricity and Vacuum for Far East
S. Južni1
1
University of Oklahoma, 401 West Brooks, Room 512,
Norman, Oklahoma 73019-0528, USA
2 Mayordoom of Kostel, Slovenia
Email: [email protected]; [email protected]
The astronomical excellence of the first rate Habsburg literati Augustin Hallerstein
was widely recognized recently.
As the prominent first rate scientist attached to the Chinese Imperial Court he was
involved in other types of research besides astronomy, but his authorship was not
always clear inside the Jesuits’ collective work. Besides astronomical observations
the Beijing Jesuits also provided early electricity experiment, which enabled Volta’s
invention of the electrophorus and battery. The development of such devices paved
the way for the longer-duration electrical observations instead of the instant ones
Leyden jar experiments. The scientists urgently needed that novelty because they
wanted to know a process hidden behind an interesting electrical sparking. The
electrics experiments became the European fashion, as the vacuum pumps were
somewhat earlier. Both entered Chinese court in Hallerstein’s time, but eventually
never received the same amount of interest as Western astronomy did. One of the
reasons for the Chinese doubts was the nonexistence of the broader scale technical
use of vacuum or electricity during Hallerstein’s lifespan. The Empress Maria
Therese’s physician Ingenhousz and other physicians educated in Leyden
eventually developed broader use of electricity in scientifically somewhat backwards
countries, as were Hallerstein’s native Habsburg monarchy or Japan.
Robert Adler:
Angewandte Physik im Bereich der Elektronenröhren
und des Ultraschalls
F. Pichler1 und H. Thim2
1
Institut für formale Modelle und Verifikation,
Johannes Kepler Universität Linz, [email protected]
2
Institut für Mikroelektronik, Johannes Kepler Universität Linz,
Der Vortrag beleuchtet die Arbeiten des aus Wien stammenden im Jahre 1939 aber
in die USA emigrierten österreichischen Physikers Robert Adler (1913-2007), die er
in seiner langjährigen Tätigkeit bei der Zenith Radio Corp. in Chicago in der Zeit
119
von 1940 bis 1987 verfasst hat. Diese betreffen die Entwicklung spezieller
Elektronenröhren, wie das von ihm erfundene Phasitron (1947), eine
Kathodenstrahlröhre für die Frequenzmodulation sowie Wanderfeldröhren. Im
Bereich des Ultraschalls hat er elektromechanische Filter entwickelt und er gilt auch
als Erfinder der Fernsteuerung zur Bedienung von Fernseh-Apparaten (1957).
Weitere Beiträge von Robert Adler behandeln das Gebiet der akustischen
Oberflächenwellen-Filter (SAW-Filter) und deren Anwendung in der Fernsehtechnik.
Robert Adler hat mehr als 50 wissenschaftliche Arbeiten verfasst und erhielt mehr
als 180 US-Patente zugesprochen. Für seine Leistungen wurde er mehrfach geehrt.
Hier ist besonders die an ihn im Jahre 1980 von IEEE verliehene Edison- Medaille
zu erwähnen. Robert Adler kann zu den bedeutendsten aus Österreich
stammenden Physikern im Bereich der Angewandten Physik und der
Nachrichtentechnik gezählt werden
„Erinnerungen an Professor Dr. Fritz Kohlrausch:“
In Memoriam Hofrat DI Franz Allmer
P.M. Schuster
Victor-Franz-Hess-Gsellschaft,
Schloss 1, 8225 Pöllau, [email protected]
Einen Tag vor der Eröffnung der ÖPG Tagung 2008 am 22. September in
Leoben erhielt der Verfasser von Hofrat DI Allmer einen Anruf und via E-Mail
zwei kurze Notizen von ihm über Prof. Dr. Fritz Kohlrausch. Er habe geplant,
diese Notizen bei derselben Tagung in Leoben vorzutragen, teilte Allmer mit, sei
wegen einer Erkrankung aber leider verhindert. Er wolle diese aber gerne dem
Verfasser übergeben um auf einen bedeutenden Physiker aufmerksam zu
machen, der noch zu wenig gewürdigt worden sei. Er arbeite intensiv über
Kohlrausch und wolle im nachfolgenden Monat mit Hilfe von Prof. Dr. Jäger, der
Kohlrausch noch persönlich gekannt hatte, seine Arbeit fertig bringen. Wenige
Tage später verunglückte Hofrat DI Franz Allmer tödlich.
Der vorliegende Beitrag widmet sich dem Werk und Leben von Franz Allmer,
der an der Sektion GEP der ÖPG seit 2006 regen Anteil genommen hatte, und
den der Verfasser bei vielen Gelegenheiten als außerordentlich kompetenten,
bis ins hohe Alter rührigen, physikhistorisch interessierten Kollegen geschätzt
hatte. Die persönlichen Erinnerungen von Hofrat DI Franz Allmer an Prof.
Dr. Fritz Kohlrausch, die bis dato unveröffentlicht sind, werden vorgetragen.
120
8.7 LHS – Lehrkräfte an Höheren Schulen
Mittwoch – Wednesday, 8 September 2010
Fachausschuss Lehrer an Höheren Schulen Scientific Committee Physics Teachers (LHS)
Parallel Session LHS
Zeit-Time
Vortragender
Lecturer
Vortragstitel
Title of Lecture
Audi Max (HS 401)
Abstracts und Details siehe pp. 29-31
13:15 - 13:30
Gerhard Haas (Neues
Gymnasium Leoben)
Roman Ulrich Sexl - Prize:
Austrian Young Physicist Tournament
13:30 - 13:45
Brigitte Pagana-Hammer
(GRg3 Wien, Fak. Physik,
Univ. Wien)
Roman Ulrich Sexl - Prize:
IYPT-Aufgaben: Eine didaktische
Herausforderung für den
Physikunterricht
AYPT- IYPT Fight Demonstration,
Physics Olympiad, PhysikFachbereichsarbeiten
13:45 - 14:15
Blauer Hörsaal (HS 402)
Fachausschusses LHS
LHS Annual General Assembly
14:15 - 14:30
14:30 - 15:00
Peter Schmid
(Univ. Innsbruck)
CERN
Neuigkeiten vom LHC und das CERN
Outreach Programm
15:00 - 15:30
Laurenz Widhalm
(ÖAW)
teilchen.at – Die OutreachInitiative des FAKT
Exkursion zum Museum Haus der
Natur und Science Center
Excursion to Museum Haus der Natur
and Science Center
16:00 - 18:00
121
LHS-1: Blauer Hörsaal, Mi, 8 Sept, 14:30 Uhr
CERN - Neuigkeiten vom LHC und das CERN Outreach Programm
P. Schmid
Institut für Astro- und Teilchenphysik, Universität Innsbruck, Technikerstr. 25,
A 6020 Innsbruck
Der Large Hadron Collider (LHC) wurde im März 2010 im CERN in Betrieb
genommen und hat seither Daten von Protonenkollisionen bei 900 GeV und 7 TeV
Schwerpunktenergie geliefert. Alle Experimente funktionieren hervorragend und
konnten bei den Sommerkonferenzen über eine große Zahl von Ergebnissen
berichten.
CERN bietet seit vielen Jahren eine breite Palette von Informationen und
Besuchsmöglichkeiten für die Öffentlichkeit [1]. Die Programme mit besonderer
Relevanz für Mittelschullehrer und –schüler [2] werden vorgestellt.
Literatur
[1]
http://public.web.cern.ch/public/en/About/About-en.html
[2]
http://education.web.cern.ch/education/
LHS-2: Blauer Hörsaal, Mi, 8 Sept, 15:00 Uhr
teilchen.at – Die Outreach-Initiative des FAKT
L. Widhalm
Institut für Hochenergiephysik der ÖAW, Nikolsdorfergasse 18, 1050 Wien
[email protected]
Im Dezember 2009 hat das FAKT Koordinationsteam beschlossen, die
Öffentlichkeitsarbeit der FAKT-Institute österreichweit zu koordinieren und zu
forcieren. Der Vortragende wurde dabei gebeten die Rolle des Koordinators zu
übernehmen, und hat in dieser Funktion alle Mitgliedsinstitute des FAKT besucht,
die bereits existierenden Outreach-Tätigkeiten erhoben und die Vernetzung der
Aktivitäten initiiert. Dieser Vortrag stellt die bereits realisierten und für die Zukunft
geplanten Projekte in Hinblick auf die Relevanz für PhysiklehrerInnen und
SchülerInnen vor, dazu zählen neben der Webpräsenz [1] auch die
Wanderausstellung „teilchen.at“ [2], die derzeit im Rahmen der ÖPG Tagung in
Salzburg zu sehen ist, und für Schulen gebucht werden kann. Weitere Programme
sind „Physik zum Anfassen“ sowie spezielle Angebote zur Begabtenförderung.
Literatur
[1] www.teilchen.at
[2] events.teilchen.at
122
8.8 MBU – Medizinische Physik, Biophysik und Umweltphysik
Fachausschuss Medizinische Physik, Biophysik, Umweltphysik Scientific Committee Medical Physics, Biophysics, and
Environmetal Physics (MBU)
Parallel Session MBU
Zeit
Time
Vortragstitel
Title of Lecture
14:25 - 14:30
Günther Schauberger
(VetMed. Univ. Wien)
Eröffnung der Fachtagung MBU Opening of the Topical Session MBU
14:30 - 15:00
Werner Schmidt
(Donauspital Wien)
Medizinische Physik 2010 in Österreich:
Was trägt die Öster. Ges. für Medizinische
Physik (OGMP) dazu bei?
15:00 - 15:15
Herbert Lettner
(Univ. Salzburg)
Dynamik und Dosimetrie
der Radonfolgeproduktablagerung
auf der Haut
15:15 15:30
Rozhin Penjweini
(Univ. Wien)
Characterizing the effects of combinations
of visible-infrared laser beam and blue/redLED-arrays on Albican candida and
Pityriasis versicolor distruction
15:30 15:50
15:50 - 16:05
Khan Alam
(Univ. Salzburg)
Variability of aerosol optical depth over
mega city Karachi
using MODIS and AERONET data
16:05 - 16:20
M. Hussain
(Univ. Salzburg)
Lung dosimetry for inhaled long-lived
radionuclides
and radon progeny
123
16:20 - 16:35
Günther Schauberger
(VetMed. Univ. Wien)
Reconstruction of the airborne emissions
by inverse dispersion modelling
and generation of synthetic emission
data by a Monte Carlo approach
16:35 16:50
Thomas Wilflinger
(Univ. Salzburg)
Altersabschätzung alpiner Kryokonite mit
Hilfe natürlicher und künstlicher
Radionuklide
16:50 17:05
Pierre Madl
(Univ. Salzburg)
Waterfall-related aerosol inventory
MBU-1: HS 415, Do, 9 Sept, 14:30 Uhr
Medizinische Physik 2010 in Österreich:
Was trägt die Österreichische Gesellschaft für Medizinische Physik
(OGMP) dazu bei?
W.F.O. Schmidt
Institut für Radioonkologie, Donauspital Wien
A 1220 Wien, Langobardenstrasse 122
[email protected]
In einem Übersichtsvortrag sollen aktuelle Aktivitäten der Österreichischen
Gesellschaft für Medizinische Physik vorgestellt werden. Dazu zählen
insbesondere:
x
Die Vorbereitung einer Dreiländertagung (Deutschland, Schweiz,
Österreich) in Wien im September 2011.
x
Fortbildungsveranstaltungen im Herbst 2010 (u. a. zu Röntgendiagnostik
und bildgebenden Verfahren).
x
Einbindung der österreichischen Medizinphysiker in gesamteuropäische
Aktivitäten wie Fort- und Weiterbildung sowie Kriterien zur wechselseitigen
Anerkennung von Medizinphysikern in Europa
x
Aktivitäten internationaler Organisationen (z. B. WHO, IAEA) mit
Bedeutung für die Medizinphysik
Darüberhinaus ist auch eine „Standortbestimmung“ der Medizinischen Physik, vor
allem auch im Rahmen der neuen europäischen Studiensysteme („Bologna“)
notwendig geworden.
Der Vortragende ist als Präsident der OGMP in diese Aktivitäten eingebunden und
kann auf die genannten Punkte ausführlicher eingehen
124
MBU-2: HS 415, Do, 9 Sept, 15:00 Uhr
Dynamik und Dosimetrie der Radonfolgeproduktablagerung
auf der Haut
H. Lettner, W. Hofmann, H. Tempfer, A. Schober und A. Hubmer
Abteilung für Physik und Biophysik, [email protected]
Fachbereich für Materialwissenschaften und Physik, Universität Salzburg
A 5020 Salzburg, Austria
In der Radontherapie werden in zunehmendem Maße die Deposition von
Radonzerfallsprodukten (Rnp) auf der Haut und deren mögliche therapeutische
Wirkung in Betracht gezogen. In beiden angewendeten Therapieformen, der
Exposition in einer Radonatmosphäre und der Anwendung von Wannenbädern mit
radonhältigem Thermalwasser, kommt es zur Ablagerung von Radonzerfallsprodukten auf der Haut, die aber entsprechend den unterschiedlichen
physikalischen Bedingungen zu unterschiedlichen Aktivitätsverhältnissen der Rnp
auf der Haut führen, die für die Dosimetrie von nicht unerheblicher Bedeutung sind.
Unter den gegebenen Therapiebedingungen sind in der Radonatmosphäre die Rnp
generell im Ungleichgewicht mit dem Radongas. Durch die Dynamik des
Aerosolwachstums wird Po-218 als mobilstes Rnp schneller auf der Haut
abgelagert als die nachfolgenden Rnp, was letztendlich zu einer Aktivitätskonzentration in der Reihe Po-218 > Pb-214 > Po-214 führt. Deponierte Rnp
verbleiben auf der Haut und wandern in tiefere Hautschichten, wo beim Zerfall auch
die biologisch relevanten Langerhansschen Zellen von den Alphateilchen erreicht
werden können. Im Unterschied zu einer Radonatmosphäre sind unter den
Bedingungen der Exposition in den Radonwannenbädern die Rnp weitgehend im
Gleichgewicht mit Radon. Nach den experimentellen Ergebnissen desorbiert ein
großer Teil der Rnp nach der Ablagerung wieder von der Haut. Dieses Verhalten
führt zu einem Aktivitätsverhältnis der Rnp, das in etwa den Verhältnissen der
Halbwertszeiten entspricht.
Ausführliche experimentelle Untersuchungen der Exposition in einer Radonatmosphäre und in Wannenbädern unter den therapeutischen Gegebenheiten in
der Gasteiner Radontherapie haben gezeigt, dass die Deposition von Rnp auf der
Haut zu erheblichen Aktivitätskonzentrationen führt. Selbst unter den Bedingungen
der Exposition in einer Radonatmosphäre überwiegt die Deposition auf der Haut die
Deposition in der Lunge um mindestens eine Größenordnung. Infolge des
Eindringens der Rnp in tiefere Hautschichten erreicht ein Teil der deponierten
Alphaenergie biologisch relevante Bereiche, die eine nähere Betrachtung dieser
Situation nahe legt. Die Ergebnisse der experimentellen Untersuchungen und die
Berechnungen zur Dosimetrie werden in dieser Arbeit vorgestellt.
References
[1]
H. Tempfer, W. Hofmann, A. Schober, H. Lettner, A. L. Dinu. „Deposition of
radon progeny on skin surfaces and resulting radiation doses in radon
therapy”, Radiat Environ Biophys, 49, 249–259. (2010).
125
MBU-3: HS 415, Do, 9 Sept, 15:15 Uhr
Characterizing the Effects of Combinations of Visible-Infrared Laser
Beam and Blue/Red-Led-Arrays on Albican Candida and Pityriasis
Versicolor Distruction
R. Penjweini 1, 2 , F. Mohajer 3, A. Geranmayeh 2, K. W. Kratky 1, and S. Saghafi 2,4
1
Physics of Physiological Processes, Faculty of Physics, University of Vienna,
2
Biophotonics Laboratory, Plasma-Physics Research Center, Research Science
Campus, IAU, Tehran, Iran
3
Physics Department, North-Tehran Campus, IAU, Tehran, Iran
4
Department of Bioelectronics, Institute of Solid State Electronics, Vienna
University of Technology, Vienna, Austria, [email protected]
This study presents the effects of combinations of non-ionizing coherent and noncoherent visible-near infrared light on destruction of Albican Candida and Pityriasis
versicolor in vivo. Considering the absorption spectra of Candida obtained using
Carry-500-scans spectrophotometer, a second harmonics of Nd:Yag laser (100mW/
3mm spot-size), a red diode laser (120 mW/ 8mm spot-size), an infrared diode laser
( 150mW/ 6mm spot size), an array of 24 Blue-LED (72mW ) and array of 20 RedLED-Array (80 mw) have been chosen as illuminating sources.
During the irradiation process, candida infections received 6, 10 and 14 J/cm2 laser
light incident doses (ID) of 532nm, 660nm and 980nm coherent beams,
respectively. Additionally, it received 2 J/cm2 ID from LED arrays (420<<470nm
and 624<<660nm).
Patients with Albican Candida had 7 sessions of illuminations and the patients with
Pityriasis versicolor had 15 sessions of illuminations (Fig.1). In addition to the ability
of photons to produce electronic excitations in chromophores, light can induce a
wave-like alternating electric field in Cndidas that interacts with polar structures. It
produces dipole transitions at different cellular and biochemical processes [1-2].
Furthermore, the Reactive Oxygen Species (ROS) production that is cytotoxic can
be increased due to this processes and it can kill the Candida cells when the
concentration becomes sufficiently high. The method is accurate, highly
reproducible and relatively inexpensive [3].
126
Fig. 1: The effects of combination of coherent (visible/infrared) and LED on Candida
References
[1] Amat, A., “The electric field induced by light can explain cellular responses to
electromagnetic energy: A hypothesis of mechanism”. Journal of
photochemistry and photobiology B: Biology 82, 152-160 (2006)
[2] Chang, WH., “Effect of pulse- burst electromagnetic field stimulation on
osteoblast cell activities”, Bioelectromagnetic 25 (6), 457-465 (2004).
[3] Luksiene, Z., “Photodynamic inactivation of harmful and pathogenic
microorganisms”. Vet Med Zootech, 26(48), 58-60 (2004).
127
MBU-4: HS 415, Do, 9 Sept, 15:50 Uhr
Variability of Aerosol Optical Depth over the Karachi mega city
using MODIS and AERONET data
K. Alam1 and T. Blaschke1
1
Department of Geography and Geology, University of Salzburg, Hellbrunnerstrasse
34, Salzburg 5020, Austria
Atmospheric aerosols play an important role in the energy balance of the earthatmosphere system. The aerosol concentration is increasing in various locations
especially in Asia because of growing population and economy, urbanization, and
industrialization. The population of the Karachi mega city in Pakistan is currently
around 13 million and is expected to reach 25 million by 2020. The rapid growth of
the city which has resulted in unregulated development and inappropriate land-use
changes has also resulted in an estimated 50% of the population living in
unplanned, poorly serviced and heavily polluted informal settlements. The lack of
an effective and efficient mass transit system means leads to increasing numbers of
vehicles on ever-more congested roads leading to increased air pollution.
In this research we examined the spatial and temporal variations of aerosol
particles over Karachi using Moderate Resolution Imaging Spectroradiometer
(MODIS) data from the Terra satellite and ground based data using Aerosol Robotic
Network (AERONET) for the year 2009. We used the Hybrid Single Particle
Lagrangian Integrated Trajectory (HYSPLIT) model for trajectory analysis to reveal
the origins of air masses, with the aim of understanding these spatial and temporal
variabilities in aerosol concentrations. Our analysis reveals that maximum values of
aerosol optical depth (AOD) are found in the summer season both for satellite and
ground based observations. We also examined the relationship between AOD and
water vapour (WV) in order to understand the hygroscopic nature of atmospheric
aerosols. The analyses exhibit strong positive correlations (greater than 0.85)
between AOD and WV. We observed that WV is also higher during the summer,
matching the increase in AOD and indicating the possibility of hygroscopic growth of
aerosols.
References
[1]
Kuniyal, C.J., Thakur, A., Thakur, K.H., Sharma, S., Pant, P., Rawat, S.P.,
and Moorthy, K.K. Aerosol optical depths at Mohal-Kullu in the northwestern
Indian Himalayan high altitude station during ICARB. J. Earth Syst. Sci, 118,
41-48 (2009).
[2]
Prasad .K.A, Singh .R.P, and Ashbindu, S. Variability of Aerosol Optical
Depth over Indian Subcontinent using MODIS data. Journal of Indian Society
of Remote Sensing, Vol. 32, No. 4 (2004)
128
MBU-5: HS 415, Do, 9 Sept, 16:05 Uhr
Lung Dosimetry for Inhaled Long-Lived Radionuclides
and Radon Progeny
M. Hussain1,2 , R. Winker-Heil1 and W. Hofmann1
1
Division of Physics and Biophysics, University of Salzburg, 5020 Salzburg, Austria
Directorate General of Safety, 44000, Islamabad, Pakistan
2
Doses delivered to the bronchial and alveolar regions of the lung following
inhalation of long-lived radionuclides depend on the initial deposition pattern as well
as on bronchial and alveolar clearance mechanisms. Up to now, the stochastic lung
dosimetry model IDEAL-DOSE considers deposition in the whole bronchial and
alveolar airway system, while clearance was restricted to bronchial airways.
However, for the inhaled of long-lived radionuclides (LLR), alveolar clearance has
also to be considered for the calculations of alveolar as well as the bronchial doses.
Thus the primary objectives of this study were (i) to develop stochastic clearance
model in the alveolar region, (ii) to calculate total lung dose contribution from LLR in
addition to short-lived Rn-222 decay progeny.
Transport rates of insoluble particles in individual respiratory airways, alveolar ducts
and sacs are based on the average transport rates proposed for the revision of the
ICRP Human Respiratory Tract Model (HRTM). Based on average transport rates,
particle residence times are calculated stochastically in the alveolar region.
Retention curves for the alveolar region, illustrating the joint effect of deposition and
clearance, were compared with available experimental data in human volunteers,
revealing good agreement between experimental data and modeling predictions.
Dose calculations for bronchial and alveolar airways were performed for inhaled
radon progeny and 238U decay products for a reference uranium ore activity
concentration. The results obtained indicate that LLR cleared from the alveolar
region are the primary contributor to bronchial doses, being higher by factors of 2-6
than the dose contributed by radionuclides directly deposited in the bronchial tree.
Comparison of LLR doses to that of short-live radon progeny predicts that long lived
alpha emitters in uranium mines can deliver up to 5 percent of the doses allowed
from the short lived radon daughters.
References
[1]
Baily, M.R.,“Updating the ICRP human respiratory tract model“, Radiation
protection dosimetry 127(1-4), 31-34 (2007)
[2]
Harley, N.H., “Alpha dose from long-lived emitters in underground mines“,
Occupational Radiation Safety in Mining 2, 518-522 (1985)
[3]
Marsh, J.W., “Dosimetric models used in the alpha risk project to quantify
exposure of uranium miners to radon gas and its progeny“, Radiation
Protection Dosimetry 130(1), 101-106 (2008)
129
MBU-6: HS 415, Do, 9 Sept, 16:20 Uhr
Reconstruction of the Airborne Emissions by Inverse Dispersion
Modelling and Generation of Synthetic Emission Data by a Monte
Carlo Approach
G. Schauberger1, M. Piringer2, W. Knauder2, E. Petz2, K. Bauman-Stanzer2
and E. Petz2
1
Molecular Physiology and Biophysics, University of Veterinary Medicine Vienna,
Veterinärplatz 1, A 1210 Vienna, Austria, [email protected]
2
Central Institute for Meteorology and Geodynamics, Department of Environmental
Meteorology, Hohe Warte 38, A 1190 Vienna, Austria, [email protected]
The determination of the emission flow of pollution sources can often not be done
directly. This can be the case if the geometry of the source is complicated, a direct
measurement will not be tolerated by the company, or a retrospective assessment
of the emission flow seems appropriate. In the absence of emission measurements,
the emission flow of the source can be assessed by inverse dispersion modelling
using ambient concentration measurements and meteorological parameters as
input. The dispersion model used is the Austrian regulatory Gauss model. This
method is applied to a thermal treatment plant. Seven chemical species (butyl
acetate, benzene, ethyl acetate, toluene, m/p-xylene, o-xylene and -pinene), are
identified as odour-relevant and measured over a period of 1½ years in the
prevailing wind direction leeward of the plant. The selected log-normal cumulative
distribution function (CDF) shows a good fit to the empirical CDF of all seven
species. The resulting odour emission is calculated by adding the odour emission of
all single species, using the individual odour threshold concentration. The odour
emission flow shows a good agreement showing the applicability of the chosen
approach to re-calculate odour emissions from measured concentrations of
chemical species.
The emission data are available however only for the wind directions for which the
measuring station is leeward of the plant. Using a Monte-Carlo model, the dataset
was completed also for wind directions for which no ambient concentration
measurements were available. The parameters for the Monte-Carlo model were
derived by the statistical analysis of the dataset. The main input variables which
determine the emission of the plant are the intermittence factor, air temperature,
wind velocity, time of the day and day of the week, which describe the working
process of the plant. For the model evaluation the ambient concentrations
calculated by the synthetic emission data were compared to the measured ambient
concentrations. After calibrating the Monte-Carlo model, the expected values and
the variances are in good agreement with the empirical data.
130
MBU-7: HS 415, Do, 9 Sept, 16:35 Uhr
Altersabschätzung alpiner Kryokonite mit Hilfe natürlicher und
künstlicher Radionuklide
T. Wilflinger1, A. Hubmer1 und H. Lettner1
1
Universität Salzburg, Abteilung Physik und Biophysik,
Fachbereich für Materialforschung und Physik,
Hellbrunnerstrasse 34, A-5020 Salzburg,
[email protected]
Als Kryokonite (aus dem Griechischen: kalter Staub) werden auf Eisfeldern durch
Windverfrachtung abgelagerte Sedimente bezeichnet, die sich durch teilweise
extrem hohe Radionuklidkonzentrationen auszeichnen. In Kryokoniten vom
Stubacher Sonnblickkees, einem temperierten Gletscher in den Hohen Tauern,
konnten die künstlichen Isotope 137Cs, 134Cs, 238Pu, 239+240Pu, 90Sr, 241Am, 60Co,
125
Sb, 154Eu, und 207Bi identifiziert werden. Unter den natürlichen Isotopen waren
unter anderem 210Pb, 7Be, und 40K erfassbar.
Künstliche Nuklide in der Umwelt entstammen in Zentraleuropa zwei Quellen, die
sich nach ihrer Isotopenzusammensetzung und in ihren Radionuklidverhältnissen
unterscheiden lassen. Die erste Quelle ist der Global Fallout, der in den
oberirdischen Waffentests Ende der Fünfziger bzw. Anfang der Sechzigerjahre
seinen Höhepunkt erreichte. Die zweite Quelle ist der Eintrag aus dem
Reaktorunfall von Tschernobyl, der ab der ersten Maiwoche 1986 zu einer enormen
Deposition künstlicher Radionuklide führte. Die Unterteilung und Alterszuordnung
der Kryokonite erfolgt vorwiegend durch Cäsium- und Plutoniumisotope bzw. deren
Radionuklidverhältnisse. Diese Methode wurde bereits an Kryokoniten des
Hallstätter Gletschers erfolgreich angewendet [1]. Die Bestimmung der Pu-Isotope
ist jedoch generell sehr zeit- und arbeitsaufwendig und in sehr alten oder sehr
jungen Kryokoniten praktisch unmöglich. Hier bietet sich als weitere Möglichkeit die
Altersabschätzung mit dem natürlichen Radionuklid 210Pb an, das als
Radonzerfallsprodukt in annähernd konstanten jährlichen Eintragsraten deponiert
wird.
An den Kryokoniten des Stubacher Sonnblickkees werden die verschiedenen
Möglichkeiten der Altersabschätzung mit Radionukliden gezeigt.
131
MBU-8: HS 415, Do, 9 Sept, 16:50 Uhr
Waterfall-Related Aerosol Inventory
P.Madl1, P.Kolarž2, A.Hartl3, M.Gaisberger3 and W.Hofmann1
1
University of Salzburg, Material Research and Physics,
Hellbrunnerstr. 34 A-5020 SBG, [email protected]
2
Institute of Physics, Pregrevica 118, RS-11080 Belgrade, [email protected]
3
Paracelsus Medical University, Institute for Physiology and Pathophysiology,
Strubergasse 21. 11, A-5020 SBG, arnulf [email protected],
[email protected]
The current study investigated the distributions of ionic-clusters and aerosols
originating from waterfalls. The 10 day measurement campaign was performed with
three portable Gerdien condensers (air-ion detectors) to monitor air-ion
concentrations [1] and a Scanning Mobility Particle sizer (SMPS), along with an
optical particle counter (OPC) to determine the size distribution of aerosols. The
size spectra covered in each measurement ranged from 0.9 to 350nm for the
negative ion concentration. Determination of negative charges using the SMPS
covered the full range, whereas the positive complement was restricted to a size
window of 0.9 to 2 nm and was determined by the detection principle of the SMPS.
Using the fully-fitted SMPS (with the neutralizer attached to the DMA) made it
possible to monitor aerosol distributions in the size window ranging from 5.5 to 350
nm. In combination with the OPC, it was possible to extend the upper threshold up
to 2 m.
The investigation revealed a distinct aerosol distribution in proximity to the falls
along with a soaring concentration of negative ions in the lowest size range below
10 nm. As expected, off-site control measurements used to monitor background
ion- and particle concentrations prompted significantly different signatures. The
increased concentration of negative intermediate ions is assumed to be due to the
so-called waterfall effect [2], in which auto-ionization due to friction, fragmentation
and charge-separation mechanisms cause free charges inside water droplets.
Fluctuation in charges and their mobility yield free ions when a droplet collides with
an obstacle. Aerosol spectra on the other hand showed a distinct “wash-out-effect”
of otherwise specific aerosol distribution in the absence of a waterfall, whereas
aerosol concentrations – especially in the lower size range below 100nm – are
elevated as condensation and agglomeration effects are suppressed due to the
cooler microclimatic conditions near the falls.
References
[1]
Kolarz P.M., Filipovi D.M., Marinkovi B.P., “Daily variations of indoor air-ion
and radon concentrations”, Applied Radiation and Isotopes 67, 2062–2067
(2009)
[2]
Laakso L., Hirsikko A., Gronholm T., Kulmala M., Luts A. and Parts T.E.
“Waterfalls as sources of small charged aerosol particles”, Atmos. Chem.
Phys. 7, 2271–2275 (2007)
132
8.9 OGD – Oberflächen, Grenzflächen und Dünne Schichten
Donnerstag - Thursday 9 September 2010 / Blauer Hörsaal
Parallel Session OGD
Zeit
Time
Vortragender
Lecturer
Vortragstitel
Title of Lecture
9:00 - 9:40
Keynote:
Frank Stefan Tautz
(FZ Jülich)
Metal-Molecule Contacts:
From Adsorption to Charge Transport
9:40 - 10:00
Margareta Wagner
(Univ. Graz)
Digging for the dewetting reconstruction
at the organic interface:
A low temperature STM study of 6P on Cu(110)
10:00 - 10:20
Lidong Sun
(Univ. Linz)
Thermally activated inversion of
pentacene/para-sexiphenyl heterostructures
on Cu(110)
Photoemission electron microscopy of the
Alexander J. Fleming
temperature dependent pre-nucleation
10:20 - 10:40
(Univ. Graz)
dynamics of sexiphenyl molecules deposited
on Cu (110)
10:40 - 11:00
Thorsten Wagner
(Univ. Linz)
Growth of D-6T on flat and vicinal
Ag(110) surfaces
11:00 - 11:30
133
Donnerstag - Thursday 9 September 2010 / Blauer Hörsaal
Zeit
Time
Vortragender
Lecturer
Vortragstitel
Title of Lecture
13:30 - 14:10
Keynote:
Michael Schmid
(TU Wien)
Metal diffusion and growth studied by STM
14:10 - 14:30
Stefanie Rund
(Univ. Linz)
Charge exchange of He+ ions
on aluminium surfaces
14:30 - 14:50
Erminald Bertel
(Univ. Innsbruck)
Low-dimensional systems on metal surfaces:
Electronic structure and phase transitions
14:50 - 15:10
Mariella Denk
(Univ. Linz)
The effect of postgrowth oxygen exposure
on the magnetic properties of Ni
on the Cu-CuO stripe phase
15:10 - 15:30
Yuri Suchorski
(TU Wien)
Reaction kinetics via PEEM imaging: laterallyresolved studies of catalytic CO oxidation
on single grains of polycrystalline Pd
15:30 - 15:50
15:50 - 16:10
Günther
Weidlinger
(Univ. Linz)
2D gas - condensed phase transition of
pentacene on Cu(110)-(2u1)O
16:10 - 16:30
Johannes Gall
(Univ. Linz)
Lattice Gas Monte Carlo Simulations of
Pentacene on Cu(110) - (2u1)O
16:30 - 16:50
Roland Resel
(TU Graz)
Structure and stability of a quinquethiophene
based self-assembled monolayer
16:50 - 17:10
Clemens
Simbrunner
(Univ. Linz)
Epitaxial growth of sexi-thiophene and
para-hexaphenyl on sheet silicates
17:10 - 17:30
Christoph Reichl
(AIT, Wien)
Experimental study on icing and condensation
on structured plates and glasses
in low speed flows
134
17:30 - 17:50
Ines Haynl
(Univ. Graz)
Cryo atomic force microscopy: A new way to
investigate elastomeric samples
Jahreshauptversammlung
des Fachausschusses OGD
OGD annual general assembly
17:50 - 18:10
Freitag - Friday 10 September 2010 / Blauer Hörsaal
Zeit
Time
Vortragender
Lecturer
Vortragstitel
Title of Lecture
9:00 - 9:20
Luca Gragnaniello
(Univ. Graz)
Ordered Arrays of NiOx nanoclusters
9:20 - 9:40
Igor Beinik
(MU Leoben)
Complementary study of ZnO nanorods
by scanning probe microscopy
9:40 - 10:00
Franz J. Schmied
(MU Leoben)
Tricking AFM to its limit
Michael MayrhoferReinhartshuber
10:00 - 10:20
(TU Graz)
10:20 - 10:40
10:40 - 11:00
Structure and Phonon Dispersion of Bi(111)
from He Atom Scattering
Daniel Primetzhofer Trace element quantification in high-resolution
(Univ. Linz)
Rutherford backscattering spectrometry
Mujeeb Ullah
(Univ. Linz)
Meyer-Neldel rule and disorder
in organic devices
135
OGD-1: Blauer Hörsaal, Do, 9 Sept, 09:00 Uhr
Metal-Molecule Contacts: From Adsorption to Charge Transport
F.S. Tautz
Institut für Bio-und Nanosysteme, Forschungszentrum Jülich, 52425 Jülich,
Germany, and Jülich Aachen Research Alliance Fundamentals of Future
Information Technology
[email protected]
Highly ordered monolayers and thin films of electrically active molecules on singlecrystal metal surfaces are excellent model systems for metal-molecule contacts.
They can be used to study fundamental properties of metal-molecule contacts,
employing a wide range of surface analytical techniques. In this talk I will give
examples of our recent work regarding structure and bonding at the organic-metal
interface [1-3], interface energetics [4], and precision measurements of current
transport through metal-adsorbed molecules using an STM tip [5].
The adsorption of large organic molecules on metal surfaces is often affected by a
sizeable contribution of van der Waals attraction to the interaction energy. This
makes theoretical simulations challenging. Precise measurements of structural
parameters of adsorbed molecules are therefore important as benchmarks for novel
simulation approaches [1]. On the other hand, with a universal theoretical
description still missing, empirical rules, such as the scaling of the adsorption height
with the substrate work function that was observed for PTCDA on noble metal
surfaces, provide important guidelines for our understanding [2]. Apart from the
molecule-substrate interaction, intermolecular interactions play an important role.
For example, networks of hydrogen bonds can influence the internal geometry of
adsorbed molecules and their adsorption height [3], whereas intermolecular
polarization screening can influence their electronic structure [4]. Adsorbed
molecules on single-crystal surfaces are also an excellent starting point for precise
and well-controlled charge transport experiments through individual molecules,
because with an STM they can be contacted at a defined position within the
molecule [5]. In this way, the influence of electron correlation on quantum transport
can be studied.
Finally, we show that if an STM is equipped with a single D2 molecule that is
confined in the STM junction [6], Pauli repulsion is probed and can be used to
record images of unprecedented resolution [7]. The chemical structure of molecules
and intermolecular bonds become visible.
References
[1] Mercurio, G. et al., “Structure and energetics of azobenzene at Ag(111):
Benchmarking semi-empirical dispersion correction approaches”, Phys. Rev.
Lett. 104, 036102 (2010).
[2]
Kilian, L. et al., “Role of intermolecular interactions on the electronic and
geometric structure of a large S-conjugated molecule adsorbed on a metal
136
[3]
[4]
[5]
[6]
[7]
surface”, Phys. Rev. Lett. 100, 136103 (2008).
Hauschild, A. et al., “Normal-incidence x-ray standing-wave determination of
the adsorption geometry of PTCDA on Ag(111): Comparison of the ordered
room-temperature and disordered low-temperature phases”, Phys. Rev. B
81, 125432 (2010).
Soubatch, S. et al., “Site-specific polarization screening in organic thin films”,
Phys. Rev. Lett. 102, 177405 (2009).
Temirov, R. et al., “Kondo effect by controlled cleavage of single-molecule
contact”, Nanotechnology 19, 065401 (2008).
Temirov, R. et al., “A novel method achieving ultra-high geometrical
resolution in scanning tunnelling microscopy”, New J Phys. 10, 053012
(2008).
Weiss, C. et al., “Imaging Pauli repulsion in scanning tunneling microscopy”,
Phys. Rev. Lett. 2010, accepted.
Digging for the Dewetting Reconstruction at the Organic Interface:
A low Temperature STM Ttudy of 6P on Cu(110)
M. Wagner, S. Berkebile, A. Fleming, T. Ules, G. Koller, F. P. Netzer
and M. G. Ramsey
Institute of Physics, Surface and Interface Physics, Karl-Franzens University Graz,
A-8010 Graz, Austria, [email protected]
From studies of the sexiphenyl (6P) growth on Cu(110) with Photoemission Electron
Microscopy (PEEM), enhanced 1-dimensional diffusion has been observed. We
have postulated this to be a result of a 3rd layer dewetting reconstruction [1,2]. In
this work with the STM at cryogenic temperatures the nature of this reconstruction
has been explored. Moreover, by applying molecular manipulation we have been
able to “dig” down through several molecular layers to the Cu interface. The initial
3rd layer molecules which we argued to provide channels for the observed 1-D
diffusion are observed as one-dimensional strings of twisted molecules. The regular
spacing of the strings suggests a reconstruction. Removing these strings and 2nd
layer molecules reveals that the highly ordered and densely packed 1st monolayer
of planar flat lying molecules on Cu(110) has been reconstructed with edge-on
planar molecules incorporated into it. Thus the reconstruction is not an organic
surface reconstruction per se but a reconstruction at the molecule-Cu interface.
This work has been supported by the by the Austrian Science Foundation (FWF)
within the National Research Network “Interface Controlled and Functionalized
Organic Films” and the ERC Advanced Grant “SEPON”.
References
[1]
Fleming A. et al., “PEEM of the Temperature Dependent Pre-nucleation
Dynamics of Sexiphenyl Molecules Deposited on Cu(110)”, Phys. Chem.
137
[2]
Chem. Phys., submitted
Fleming, A. et al., “Pre-Nucleation Dynamics of Organic Molecule SelfAssembly Investigated by PEEM“, Omicron, Result of the month 06/2010
Thermally Activated Inversion of
Pentacene/Para-Sexiphenyl Heterostructures on Cu(110)
L.D. Sun1, C.Y. Liu1,2, D. Queteschiner1, G. Weidlinger1, X. Fu2, X.T. Hu2
and P. Zeppenfeld1
1
Institute of Experimental Physics, Johannes Kepler University Linz
Altenbergerstr. 69, A-4040 Linz (Austria), [email protected]
2
State Key Laboratory of Precision Measuring Technology and Instruments,
Tianjin University, Weijin Road, 300072 Tianjin, (China)
Thermally activated inversion of pentacene/para-sexiphenyl (p-6P) molecular
heterostructures on the Cu(110) surface is studied with the combination of
reflectance difference spectroscopy (RDS) and scanning tunnelling microscopy
(STM). The heterostructures are formed by deposition of a sub-monolayer of
pentacene on top of a p-6P buffer layer with a thickness of up to 3 monolayers on
Cu(110) at 15 K. When the sample temperature is raised, these heterostructures
invert, with pentacene molecules diffusing through the p-6P buffer layer and getting
in direct contact with the substrate. The observed inversion is due to the energy
minimization of the multilayer system and is thus of general importance for organic
heterostructures. The onset temperature of the inversion increases with the number
of p-6P monolayers indicating a corresponding rise of the energetic barrier for the
inter-layer diffusion.
Photoemission Electron Microscopy of the Temperature
Dependent Pre-nucleation Dynamics of Sexiphenyl
Molecules Deposited on Cu (110)
A. J. Fleming, S. Berkebile, F. P. Netzer and M. G. Ramsey
Surface and Interface Physics, Karl-Franzens Universität Graz, Universitätsplatz 5, 8010 Graz, Austria
[email protected]
The pre-nucleation dynamics of sexiphenyl (6P) molecules deposited in-situ on Cu
(110) is investigated by photoemission electron microscopy (PEEM) in ultrahigh
vacuum. PEEM, in threshold mode, is used to monitor precisely in real-time a) the
138
amount deposited, b) layer filling by 6P molecules, c) dynamic surface density
redistributions during layer filling and d) critical surface density spontaneously
induced meta-stable layer de-wetting [1]. It is by studying this crucial pre-nucleation
deposition period that the requirements for critical nucleation of 6P, can be
understood. A numerical simulation of PEEM image photoemission intensity
variations with time is shown to help determine pre-nucleation layer filling
mechanisms for various growth temperatures. Comparison with data previously
obtained from static techniques, such as STM and LEED, together with dynamic
data from PEEM of 6P deposited on Cu (110) 2 x 1 – O [2] enable the 6P nucleation
processes to be elucidated from PEEM. Furthermore, data obtained during postnucleation deposition times allows nucleation and molecular binding energies to be
obtained from temperature dependent trends of nucleation and desorption rates,
respectively.
References
[1]
Omicron June 2010 Result of the Month, Omicron Nanotechnology,
www.omicron.de
[2]
A J Fleming, F P Netzer, M G Ramsey, J. Phys: Condens. Matter 21 (2009)
445003
Growth of D-6T on Flat and Vicinal Ag(110) Surfaces
T. Wagner1,2, D. R. Fritz1 and P. Zeppelfeld1
1
Johannes Kepler University Linz, Institute for Experimental Physics, Atomic
Physics and Surface Science Division, Altenbergerstr. 69, 4040 Linz
2
For the growth of D-sexithiophene (D-6T) on a variety of substrate surfaces a
Stranski-Krastanov growth is reported: After the completion of a wetting layer, 3D
crystallites are formed. It is known that the crystallographic structure of the
crystallites is strongly influenced by the substrate: Ivanco et al.[1] have changed the
orientation of the molecules from flat lying to upright standing by inducing defects to
the surface by ion bombardment. To determine the influence of the substrate
morphology on the structure of an organic film we have studied the growth of D-6T
on a flat Ag(110) and stepped Ag(441) crystal surface by means of photoelectronemission microscopy (PEEM) and scanning tunnelling microscopy (STM).
The PEEM technique allows studying the growth in situ and in real time. The
coverage dependent intensity curves recorded on Ag(110) and Ag(441) with an Hg
lamp (4.9 eV) are almost identical: Although the ionisation potential of the D-6T is
higher than the energy of the photons, a uniform increase of the PEEM intensity is
found upon the deposition of the first layer because of a lowering of the work
function at the metal-organic interface. Additional layers on top do not contribute to
the electron emission but scatter electrons emitted from the metal-organic interface.
139
Therefore, the PEEM intensity decreases again for the second and further layers.
Only if one uses photon sources with higher energies like a D2 (6.4 eV) or a He
lamp (21.2 eV) one can excite photoelectrons from the organic layer itself. For the
same sample temperature, larger but fewer crystallites are found on the flat Ag(110)
surface as compared to the Ag(441) surface where the step edges act as
nucleation centres. PEEM spectroscopy further reveals that besides the wetting
layer there are two types of crystallites present on the Ag(110) surface: Needle like
crystallites consisting of flat lying molecules and platelets, in which the molecules
are nearly upright standing.
For the initial growth of D-6T on Ag(110) we find two orientations of the molecules in
the first layer by STM: They arrange parallel to the [001] and [1-10] direction while
no long range order is found. For the second layer of D-6T on the Ag(110) surface,
the molecules align in chains with their long axis parallel to the [001] direction. For
the Ag(441) surface, the orientation of the molecules is exclusively parallel to the [110] direction in the first and second layer, i.e., the molecules align parallel to the
silver steps. In addition step bunching and faceting of the substrate surface occurs
due to the adsorption of D-6T.
References
[1]
J. Ivanco, T. Haber, J.R. Krenn, F.P. Netzer, R. Resel, M.G. Ramsey,
“Sexithiophene lms on ordered and disordered TiO2(110) surfaces:
Electronic, structural and morphological properties”, Surface Science 601,
178-187 (2007)
Metal Diffusion and Growth Studied By STM
M. Schmid
Institut für Angewandte Physik, TU Wien, 1040 Wien, Austria.
[email protected]
The structure and morphology of thin films grown by deposition on solid surfaces
strongly depend on two elementary processes, diffusion and nucleation. While
these processes are very rapid at typical conditions used for thin film growth, we
can study them in detail by scanning tunneling microscopy at low temperatures and
submonolayer coverages. Even though such studies have been conducted for
about two decades [1], surprising results are still possible in this field.
The first part of the talk will be devoted to nucleation theory applied to metal
homoepitaxy by pulsed laser deposition (PLD). PLD differs from thermal
evaporation (physical vapor deposition) by the high instantaneous flux of particles
arriving at the surface and by high-energy ions (30 ... 300 eV) impinging on the
surface, both leading to increased nucleation densities [2]. STM shows defects
created by the high-energy ions, which is also of interest for other deposition
140
methods like ion-beam assisted deposition (IBAD) and sputter deposition, where
the effects of fast ions are not easily accessible to experiment.
In the second part, new effects in metal diffusion and nucleation will be presented.
We will show that the long-range forces acting on adatoms play an important role
that has been often ignored in such studies. By watching adatom diffusion of Co
and Pt on Pt(111), we found a barrier for formation of Co ad-dimers, while Pt
adatoms easily form dimers. Density functional theory (DFT) calculations show that
the barrier is not related to the magnetic moment of Co atoms.
Nucleation of small Pt clusters shows another unexpected phenomenon: We found
a large number of linear chains, with lengths of up to 9 atoms. This result cannot be
explained by a simple diffusion-limited-aggregation model, and we suggest that the
strain field of the substrate plays an important role, steering some of the diffusing
adatoms towards the ends of linear clusters. As a further ingredient to this
phenomenon, a study of the binding energies of Pt adatom clusters by DFT shows
that bonding of such clusters does not follow the rule of "higher coordination means
stronger bonding". Instead, short linear chains are bound more strongly than more
compact configurations. The reason for this phenomenon is strong directional
bonding via dz2-like orbitals, a mechanism previously proposed for binding between
the late transition metals and oxygen atoms and explaining the preference for O
atoms at opposite sides of a metal atom [3].
References
[1]
[2]
[3]
Michely, T, Krug J, “Islands, mounds and atoms – patterns and processes in
crystal growth far from equilibrium“, Springer Berlin 2004
Schmid M. et al., “High island densities in pulsed laser deposition: causes
and implications”, Phys. Rev. Lett. 103, 076101 (2009).
Lundgren, E. et al., “Surface oxides on close-packed surfaces of late
transition metals”, J. Phys.: Condens. Matter 18, R481 (2006).
Charge Exchange of He+ Ions on Aluminium Surfaces
S. Rund*, D. Primetzhofer, S.N. Markin and P. Bauer
Institut für Experimentalphysik, Johannes Kepler Universitaet Linz, A-4040 Linz
INTRODUCTION
The efficient neutralization of low energy ions scattered from surface atoms is the
basis of the superior surface sensitivity in Low-Energy Ion Scattering (LEIS) [1].
Below a reionization threshold Eth non-local Auger neutralization (AN) is the only
relevant charge exchange process and permits to describe the ion fraction P+ by
P
f
v
exp( ³ *A ( z (t )) dt ) { exp( c ) with the Auger transition rate A, the
vA
0
141
characteristic velocity vc and the velocity of the projectile perpendicular to the
surface v. At primary energies E > Eth local charge exchange processes, i.e.
collision induced reionization (CIR) and collision induced neutralization (CIN) start
to contribute.
EXPERIMENTAL RESULTS
An Al(111) single crystalline surface and polycrystalline aluminium have been
investigated by electrostatic analyzer low-energy ion scattering (ESA-LEIS) using
³He+ and 4He+ ions. Experiments were performed with the set up MiniMobis which
permits precise analysis of the energy of ions backscattered in single collision from
surface atoms at very low primary energies (down to 280 eV).
1
3
70
He - Al/Si
4
He - Al/Si
4
He - Cu [S. Markin]
50
FWHM, eV
=2
.2x
He oAl(111)
10
5
m/
s
+
c
Ion fraction P
60
v
40
30
20
0,1
0,01
4
He
He
10
3
0
0,0
0,5
d 0,2
Fig. 1:
1,0
1,5
2,0
2,5
0,0
3,0
-6
5,0x10
kE0, keV
-5
1,0x10
-5
1,5x10
-5
2,0x10
1/vA, s/m
FWHM of the detected ion intensity Fig. 2:
backscattered from Al (squares) and
Cu (triangles).
Experimentally deduced ion
fraction P+ of He+ scattered
from Al(111)
The reionization threshold Eth was deduced from the energy dependence of the
FWHM of the ion peak. For Cu where AN dominates up to 2 keV E~E is observed
[2], as expected for an ESA. In contrast, the FWHM of the ion peak in spectra
recorded for He+ and Al exhibits a significant broadening at 0.2– 1 keV (see Fig. 1).
Since reionization leads to an energy loss (~ 15 – 20 eV) the increasing contribution
of CIR will also increase the FWHM and additionally shift the ion peak to smaller
energies. Extrapolating data points of 4He and 3He scattered from Al/Si at higher
energies one obtains Eth = 200 eV. The experimentally deduced P+ is depicted in
Fig. 2. Although all data presented are recorded at E > Eth, very good agreement
with a fit according to Eq. 1 is found. No significant deviation is observed even for
the highest energies, pointing to a qualitatively different neutralisation behaviour
than for Cu were a strong deviation was observed for E > Eth [2].
References
[1] H.H. Brongersma, M. Draxler, M. de Ridder, P. Bauer, Surf. Sci. Rep. 62
(2007) 63.
[2] M. Draxler, R. Gruber, H.H. Brongersma, P. Bauer, Phys. Rev. Lett. 89 (2002)
263201
142
-5
2,5x10
Low-Dimensional Systems on Metal Surfaces:
Electronic Structure and Phase Transitions
E. Bertel1, M. Cordin1, P. Amann1, A. Menzel1, and J. Redinger2
1
Institute of Physical Chemistry, University of Innsbruck, A-6020 Innsbruck, Austria;
[email protected]
2
Institute of Applied Physics, Vienna University of Technology, A-1010 Wien,
Austria
Lowering the dimensionality of electronic systems increases electronic correlation
and often leads to instabilities caused by competing electronic interactions. In the
ideal case of one-dimensional (1D) systems, the Fermi liquid paradigm breaks
down in favour of Luttinger liquid behaviour. The phase diagram of real (quasi-1D)
systems depends on the relative strength of interactions and is in most cases only
partially understood [1]. The (110) surfaces of Pt and Pd fcc single crystals feature
strongly anisotropic electronic surface resonances and are therefore well-suited
templates to prepare quasi-1D systems [2]. We investigate these systems by angleresolved UV photoemission and scanning tunnelling microscopy. Although
correlation is expected to be weak on a metal surface, a strongly enhanced
electron-phonon interaction is observed in the present low-D systems. Competition
between inter-adsorbate interactions and charge density wave formation in the
substrate leads to an anomalous phase diagram on both metal surfaces [3-4].
Furthermore, tuning the electronic surface structure via suitable adsorbates seems
to result in a ferromagnetic surface layer on the Pd(110) surface. Such a layer has a
profound effect on the transmission and reflection of spin polarised electrons.
Hence a reversible switching of a surface layer into a ferromagnetic state could
have attractive applications in spintronics.
References
[1]
Bertel, E. and A. Menzel, Nanostructured surfaces: Dimensionally
constrained electrons and correlation, in The Oxford Handbook of
Nanoscience and Technology, A.V. Narlikar and Y.Y. Fu, Editors.,
308-354, Oxford University Press (2010)
[2]
Dona, E., et al., Nanostructured metal surfaces as quasi-one-dimensional
model systems. Applied Surface Science 254(14), 4230-4237 (2008)
[3]
Dona, E., et al., Fluctuations and phase separation in a quasi-onedimensional system. Physical Review Letters 98(18) 186101-4 (2007)
[4]
Cordin, M., et al., Phase transitions driven by competing interactions in
low-dimensional systems: A microscopic view. submitted (2010).
143
The Effect of Postgrowth Oxygen Exposure on the Magnetic
Properties of Ni on the Cu-CuO Stripe Phase
M. Denk, R. Denk, M. Hohage, L. Sun, and P. Zeppenfeld
Institut für Experimentalphysik, Johannes Kepler Universität Linz, A-4040 Linz,
Austria; E-Mail: [email protected]
The magnetism and morphology of thin Ni films deposited on clean and oxygen
covered Cu(110) has been studied. In the latter case oxygen acts as a surfactant
modifying the Ni growth.
Scanning Tunneling Microscopy (STM), as well as Reflectance Difference
Spectroscopy (RDS) are used to characterise the sample properties. The sensitivity
of the RDS to the polar Magneto-Optic Kerr Effect has been exploited (RD-MOKE).
Contrary to growth on pristine Cu(110), thin Ni films on oxygen covered Cu(110)(2x1)O show a spin reorientation transition from in-plane to out-of-plane
magnetisation at 9 ML Ni coverage [1], [2].
For Ni films evaporated on the Cu-CuO stripe phase, which consists of a periodic
array of (2x1) reconstructed CuO stripes separated by bare Cu, the magnetic easy
axis lies completely in-plane up to a coverage of 22.5 ML. Exceeding this coverage,
a small remanent magnetisation component pointing out-of-plane evolves. Upon
postgrowth oxygen exposure the Ni film becomes completely out-of-plane
magnetised and the out-of-plane remanence and coercive field strongly increase
during exposure. STM images show a fully (2x1)O reconstructed surface after the
oxygen exposure, but no morphological changes of the Ni film. We thus conclude
that the oxygen strongly modifies the surface magnetic anisotropy.
References
[1]
Th. Herrmann, K. Lüdge, W. Richter, K. G. Georgarakis, P. Poulopoulos,
R. Nünthel, J. Lindner, M. Wahl and N. Esser, Phys. Rev. B, 73, p. 134408
(2006)
[2]
R. Denk, M. Hohage and P. Zeppenfeld, Phys. Rev. B, 79, p. 073407 (2009)
144
Reaction Kinetics via PEEM Imaging: Laterally-Resolved Studies of
Catalytic CO Oxidation on Single Grains of Polycrystalline Pd
Y Suchorski1, Ch. Spiel1, D. Vogel1,2, W. Drachsel1, R. Schlögl2, G. Rupprechter1
1
Institute of Materials Chemistry, Vienna University of Technology,
A-1210 Vienna, Austria
2
Fritz-Haber-Institut der Max-Planck-Gesellschaft, D-14195 Berlin, Germany
To describe the catalyst behavior, studies of reaction kinetics are often summarized
in a so-called kinetic phase diagram, in which the regions of monostability,
bistability and temporal oscillations are displayed for various external parameters.
Such kinetic studies are mainly performed by mass-spectroscopy (MS) and suffer,
for heterogeneous systems, from spatial averaging. As a result, the obtained kinetic
phase diagram presents a superposition of reactive properties of different surface
regions which may differ significantly from each other, e.g. for metal-oxide systems
[1].
However, kinetic transitions in a catalytic reaction can not only be pursued by MS
techniques but also by in situ visualization of the reaction using modern surface
microscopies, such as PEEM (photoemission electron microscopy, [2,3]). However,
corresponding diagrams are generally created by spatial averaging of the PEEM
data, similar as for MS, and the main advantage of PEEM, namely the possibility to
obtain laterally-resolved information, was not yet exploited for locally-resolved
kinetic studies.
Recently, we have demonstrated for the first time that kinetic phase diagrams can
also be obtained for individual m-sized domains of a polycrystalline Pt foil, by
processing the video-PEEM data obtained during catalytic CO oxidation [3]. In
present contribution we extend this approach to polycrystalline Pd foil. We were
able to obtain the kinetic phase diagrams for the [100]-, [110]- and [111]-oriented
domains, present on the polycrystalline Pd foil. The differences between the Pt and
Pd domains of the same orientation with respect to CO oxidation and effects of
reaction-coupling between the domains are discussed.
References
[1]
Y. Suchorski, R. Wrobel, S. Becker, H. Weiss, J. Phys. Chem. C, 112 (2008)
50, and refs. therein.
[2]
G. Ertl, Nobel Prize Lecture, Ang. Chemie Int. Ed. 47 (2008) 3524; M.
Berdau, G.G. Yelenin,
A. Karpowicz, M. Ehsasi, K. Christmann, J.H. Block, J. Chem. Phys. 110
(1999) 11551.
[3]
Y. Suchorski, Ch. Spiel, D. Vogel, W. Drachsel, R. Schlögl, G. Rupprechter,
2010, submitted.
145
2D gas - Condensed Phase Transition of Pentacene on Cu(110)-(2x1)O
G. Weidlinger1, C.Y. Liu1,2, D. Queteschiner1, L.D. Sun1,
X. Fu2, X.T. Hu2 and P. Zeppenfeld1
1
Institute of Experimental Physics, Johannes Kepler University Linz,
Altenbergerstr. 69, A-4040 Linz (Austria), [email protected]
2
State Key Laboratory of Precision Measuring Technology and Instruments,
Tianjin University, Weijin Road, 300072 Tianjin, (China)
The adsorption of pentacene on Cu(110)-(2x1)O in the sub-monolayer regime was
studied in-situ using reflectance difference spectroscopy (RDS). In a wide
temperature range, the RD signal recorded as a function of pentacene coverage
reveals a change of the preferential orientation of the long molecular axis from the
Cu[1-10] at low coverage to the Cu[001] direction at high coverage. The observation
is explained by a phase transition from a 2D gas phase to a 2D condensed phase
accompanied by the switching of the molecular orientation. From the variation of the
critical coverage of the phase transition as a function of substrate temperate, the
interaction energy of pentacene in the condensed phase on Cu(110)-(2x1) is
determined to be about 84 meV.
Lattice Gas Monte Carlo Simulations of Pentacene on Cu(110) - (2u1)O
J. Gall1, M. Hohage1, C. Liu1, D. Queteschiner1, G.Weidlinger1, L. Sun1,
and P. Zeppenfeld1
1
Institute of Experimental Physics, Johannes Kepler University, Linz, Austria.
[email protected]
A reversible two-dimensional phase transition of pentacene sub-monolayer films on
the Cu(110) - (2u1)O reconstructed surface has been observed. Several Monte
Carlo (MC) and Kinetic Monte Carlo (KMC) simulations of a lattice gas model have
been performed to understand the behavior of the system.
The combination of MC and KMC simulations allows investigating the role of kinetic
processes during the phase transition. In the simulations different interaction
models have been investigated. In particular, we find that the characteristics of the
phase transition strongly depend on the anisotropy of the lateral interactions.
The simulation results are compared to recent RDS (reflectance difference
spectroscopy) and STM (scanning tunneling microscopy) experiments as well as to
theoretical results from Onsager [1].
146
References
[1]
Onsager, L., Crystal statistics. I. A two-dimensional model with an orderdisorder transition. Phys. Rev., 65 (1944), 117.
Structure and Stability of A Quinquethiophene
Based Self-Assembled Monolayer
H.-G. Flesch1, A. Moser1, O. Werzer1, E.C.P. Smits2,3,4, S. G. J. Mathijssen3,
F. Gholamrezaie2,3, H.J. Wondergem3, S.A. Ponomarenko5, D.-M. Smilgies6,
G. Hlawacek7, Q. Shen7, C. Teichert7, P. Puschnig8, R. Resel1, and
D.M. de Leeuw2,3
1
Institute of Solid State Physics, Graz University of Technology, Petersgasse 16,
8010 Graz, Austria
2
Molecular Electronics, Zernike Institute for Advanced Materials, University of
Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
3
Philips Research Laboratories, High Tech Campus 4, 5656 AE Eindhoven,
The Netherlands
4
Dutch Polymer Institute, PO Box 902, 5600 AX Eindhoven, The Netherlands
5
Enikolopov Institute of Synthetic Polymer Materials, Russian Academy of
Sciences, Profsoyuznaya 70, 117393 Moscow, Russia
6
CHESS Centre, Cornell University, 14850 Ithaca, New York, USA
7
Institute of Physics, University of Leoben, Franz Josef Strasse 18, 8700 Leoben,
Austria
8
Chair of Atomistic Modelling and Design of Materials, University of Leoben, Franz
Josef Strasse 18, 8700 Leoben, Austria
In organic electronics the use of self-assembly is one promising approach to high
yield and reproducibility in device fabrication. Quinquethiophene SAMFETs have
been built with a yield of one. Accordingly integrated circuits like bit generators
could be realized [1]. Two elements of the molecule are crucial for the monolayer
formation and the electronic properties. First the monofunctional anchoring group
which avoids uncontrolled polymerization and second the high tendency of
quinquethiophene to form nice lateral crystallographic order. This highly ordered
system is responsible for the charge transport properties within the self assembled
monolayer. Electronic and crystallographic properties have been investigated for
the submonolayer state [2]. It is the first system reported with a long range ordered
self-assembled monolayer formed on SiO2.
The formation of monolayers has been followed by atomic force
microscopy and x-ray reflectivity. However a slight tendency to form multilayers has
been found by AFM. The in-plane order of the monolayer has been investigated by
grazing incidence in-plane diffraction which reveals three nicely pronounced Bragg
rods already in the submonolayer state. From the in-plane order a herringbone
packing of the molecules within a rectangular unit cell is deduced. DFT calculations
147
have been performed to calculate the packing of the molecules within the unit cell
determined by the experiments. Two different phases can be seen in the crystal
ordering, one consisting of upright standing molecules and another one where the
molecules are tilted 13° towards the b-axis of the unit cell. A transition between
these phases is forced by temperature treatment of the SAM. In the pristine state
right after preparation in the solution the molecules are standing upright. After the
first temperature treatment (330K) they are found to be already tilted. At elevated
temperatures however the molecules are always standing fully upright. The
crystallographic order is lost above 520K, followed by a dramatic decrease in layer
thickness at 620K and complete desorption above 880K.
References
[1]
E.C.P. Smits et al., “Bottom-up organic integrated circuits”, Nature 455,
956-959 (2008)
[2]
S.G.J. Mathijssen et al., “Monolayer coverage and channel length set the
mobility in self-assembled monolayer field-effect transistors“,Nature
Nanotechnology 4, 674 - 680 (2009)
Epitaxial Growth of Sexi-Thiophene and Para-Hexaphenyl
on Sheet Silicates
C. Simbrunner1, G. Hernandez-Sosa1, D. Nabok2, M. Oehzelt3, T. Djuric4,
R. Resel4, L. Romaner2, P. Puschnig2, C. Ambrosch-Draxl2, I. Salzmann5,
G. Schwabegger1, I. Watzinger1 and H. Sitter1
1
Institute of semiconductor and solid state physics, JKU Linz, 4040 Linz,
[email protected]
2
Chair of Atomistic Modelling and Design of Materials, MU Leoben, 8700 Leoben
3
Institute of Experimental Physics, JKU Linz, 4040 Linz
4
Institute of Solid State Physics, TU Graz, 8010 Graz
5
Institut für Physik, Humboldt-Universität zu Berlin, D-12489 Berlin
Organic molecules provide several advantages in the fabrication of nanostructures,
as they combine high luminescence efficiency, flexible spectroscopic properties and
easy processing with the possibility for controlled, self-assembled growth [1].
Consequently during the last years strong efforts have been undertaken to study
the growth of thiophenes and phenylenes on various substrates, motivated by their
affinity to form highly crystalline organic nano-needles [2]. In particular, it turned out
that oligo-p-phenylenes in combination with muscovite mica as growth substrate
represent a prominent and outstanding material combination, forming a stable
molecular building block [3]. It has been demonstrated that their ability for
generating long, parallel-aligned nanofibers provides a proper fundament for
several applications like waveguiding and lasing [4]. Motivated by this promising
criterion the growth of para-hexaphenyl (p-6P) on muscovite mica has been
148
investigated intensely [5,6] and, as a consequence, the discussed material system
is well understood concerning morphological, structural and optical properties.
Contrary, the growth of phenylenes and thiophenes on phlogopite mica is rarely
analysed with respect to structural investigations.
This contribution is focused on a structural determination and analysis concerning
the epitaxial relationship between para-hexaphenyl/sexi-thiophene and
muscovite/phlogopite mica substrates. Based on x-ray diffraction experiments, a
clear picture concerning crystal phase, contact plane, azimuthal orientation and
molecular alignment can be drawn for all four material systems. All results are
verified by Fourier analysis deduced from morphological investigations which are
based on atomic force microscopy and optical microscopy leading to a consistent
picture. Based on this experimental evidence and results from force field
simulations for the adsorption of single molecules on mica substrates, an growth
model is presented being able to explain the epitaxial alignment of organic
molecules on muscovite mica substrates without the presence of dipole fields.
References
[1]
Balzer, F.; Rubahn, H.-G. “Growth Control and Optics of Organic
Nanoaggregates”,
Adv. Funct. Mat. 15, 17 (2005)
[2]
Koller, G.; Berkebile, S.; Krenn, J. R.; Tzvetkov, G.; Hlawacek, G.; Lengyel,
O.; Netzer, F. P.; Teichert, C.; Resel, R.; Ramsey, M. G., “Oriented
Sexiphenyl Single Crystal Nanoneedles on TiO2 (110)”, Adv. Mat. 16, 2159
(2004).
[3]
Schiek, M.; Balzer, F.; Al-Shamery, K.; Lützen, A.; Rubahn, H.-G., “ Lightemitting organic nanoaggregates from functionalized p-quaterphenylenes”,
Soft Matter 4, 277 (2008)
[4]
Quochi, F, “Random lasers based on organic epitaxial nanofibers”, J. Opt.
12, 024003 (2010)
[5]
Resel R., Haber T., Lengyel O., Sitter H., Balzer F. and Rubahn H.-G.,
„Origins for epitaxial order of sexiphenyl crystals on muscovite (001)“, Surf.
Interface Anal. 41, 764 (2009)
[6]
Hernandez-Sosa G., Simbrunner C. and Sitter H., “Growth and optical
properties of -sexithiopene doped para-sexiphenyl nanofibers”, Appl. Phys.
Lett. 95, 013306 (2009)
149
Experimental Study on Icing and Condensation on Structured Plates
and Glasses in Low Speed Flows
C. Reichl1, G. J. Pauschenwein1, B. Windholz1, C. Zauner1, M. Chouiki2,
R. Schöftner2 and M. Monsberger1
1
Austrian Institute of Technology, Energy Department, Giefinggasse 3,
A-1210 Wien, Österreich, [email protected]
2
Profactor GmbH, Functional Surfaces and Nanostructures, Im Statgut A2, 4407
Steyr-Gleink, Austria
Icing and condensation are critical phase change processes occurring in heat
exchanger applications as well as in solar thermal collector physics. Ice growth in
heat exchangers lead to blocking of air flow and reduce the efficiency, droplets and
ice can have a significant impact on solar production and dropping liquids can lead
to a considerable deterioration of chemically treated metal sheets often found in
those devices.
Therefore it is of utmost importance to understand condensation and the onset of
icing and its dependence on relative humidity, flow speed, turbulent structures in the
flow and both the surrounding and the plate temperature. In this contribution we
focus on the promising application of microstructures and the utilization of different
glass surfaces. An experimental facility to investigate icing and condensation in low
speed flows using thermography and image capturing methods is presented. The
facility is characterized with respect to local thermodynamic and flow properties
using various experimental techniques including CTA, 3D-PIV, surface temperature
sensors and heat sphere probes. The experimental setup and the most important
results are summarized in the first part. We will include results from thermocouple
and pt100 difference measurements. Then we will present a computational analysis
method to gain insight into the data of the image capturing during the underlying
phase change processes. This methodology is finally applied to plates and glasses
exhibiting different surface structures.
The results will add to the understanding of condensation and icing processes on
micro structured plates and glasses and provide the base for numerical simulations,
which will be capable of predicting onset-times, film- and ice-thickness estimations
leading to energy efficient and cost-effective designs.
References
[1]
Lee K., Jhee S., Yang D. (2003), Prediction of the frost formation on a cold
flat surface, International Journal of Heat and Mass Transfer 46(20), 37893796.
[2]
Reichl, Ch. et al., Experimental studies on the icingonset on plates in low
speed flows, IIR 1st Conference on Sustainable Refrigeration and Heat
Pump Technology, Stockholm, May 2010
150
Cryo Atomic Force Microscopy: A New Way to Investigate
Elastomeric Samples
I. Haynl1, A. E. Efimov2, N. B. Matsko1 and W. Grogger1
1
Graz Centre for Electron Microscopy (ZFE) & Institute for Electron Microscopy and
Fine Structure Research (FELMI) of Graz University of Technology, Steyrergasse
17, 8010 Graz, Austria, [email protected]
2
Nano Scan Technology Ltd., Zavodskaya st. 7, Dolgoprudnyy, Moscow region,
141700, Russia
The sectioning of samples at low temperatures down to -190°C is known as cryoultramicrotomy. Combined with an atomic force microscope (AFM) operating at the
same temperature this is a new method that offers great possibilities to investigate
soft materials, e.g. polymers. We are encouraged to share the results of AFM
measurements, done at room temperature and under cryo conditions, to point out
new opportunities in material characterization.
One crucial influence on the quality of measurements is sample preparation by
ultramicrotomy. Since we use elastomers, ultramicrotomy has to be operated under
cryo conditions due to the fact that soft polymers usually have a glass transition
temperature significantly below 0°C and most elastomers and their composites can
only be sectioned at temperatures 10 to 20 degrees lower than their glass transition
temperature [1]. By comparing block faces after sectioning, done at room
temperature and under cryo conditions it is easy to see how the quality of the
surfaces and therefore the AFM image quality is improved.
Preparation of a sample with the ultramicrotome and measuring the bulk surface
right after, both under cryo conditions, lead to new observations. Measuring at room
temperature would imply heating up of the sample and therefore changes in the
internal structure. It is now the first time that we are able to observe polymers in the
cryo state and prevent the samples from changes between sectioning and
measuring. We would like to discuss these results by looking at experiments done
using different elastomeric polymer blends.
References
[1]
Ivanov, D. A. and Magonov, S. N., “Atomic Force Microscopy Studies of
Semicrystalline Polymers at Variable Temperature”, (Reiter, G. and Sommer
J.-U., (Eds)), Lecture notes in physics 606, 98-130, Springer-Verlag Berlin
Heidelberg (2003)
151
OGD-17: Blauer Hörsaal, Fr, 10 Sept, 09:00 Uhr
Ordered Arrays of NiOx Nanoclusters
L.Gragnaniello*, T. Ma, S. Surnev and F. P. Netzer
Institut für Physik, Oberflächen- und Grenzflächenphysik,
Karl-Franzens Universität Graz, Universitätsplatz 5, A-8010 Graz, Austria
*[email protected]
The fabrication of ordered assemblies of nanoparticles (NPs) with uniform size of a
few nanometers presents one of the most exciting challenges in nanoscience, since
novel physical and chemical properties can be expected due to their reduced
dimensionality and due to interface and proximity effects. While promising results
have been achieved in the selfassembly of ordered metal and semiconductor NPs,
only little progress has been made until now in the 2D organization of metal oxide
nanoclusters, although potential applications are foreseen in the fields of catalysis
and magnetic applications. In particular, nickel oxide NPs are promising because of
their versatile catalytic properties [1] and because of their spin glass magnetic
behaviour [2]. Also, partially oxidized nickel clusters may be of great interest, if a NiNiO core-shell configuration is achieved, since exchange bias phenomena may
evolve [3].
Here we report the successful fabrication of ordered arrays of NiOx nanoclusters,
achieved by post-oxidation of highly ordered nickel NPs supported on an ultrathin
alumina template. The alumina substrate (2 monolayers thick) has been prepared
by controlled high-temperature oxidation of a Ni3Al(111) single crystal surface. The
complex AlOx structure [4] provides an ordered lattice of hole sites, which act as
anchoring sites for the Ni NPs condensing them into a regular superlattice with 4.1
nm dimensions. The regular arrangement of the clusters as well as their narrow size
distribution have been probed by Scanning Tunneling Microscopy and LEED. The
progressive oxidation of the Ni nanoclusters has been studied as a function of the
cluster size and the thermodynamic oxidation variables by high-resolution XPS with
use of synchrotron radiation (MAX-Lab, Lund, Sweden). We find that a morphology
conserving oxidation procedure is possible and that the resulting NiOx NPs form a
highly regular superlattice.
Work supported by the ERC Advanced Grant SEPON.
References
[1]
Wei W., et al., Journal of Hazardous Materials 168, 838–842 (2009);
Li J., et. al., Environmental Science & Technology 42 (16),
6224–6229 (2008)
[2]
Bisht V., Rajeev K.P., J. Phys.: Condens. Matter 22, 016003 (5p) (2010)
[3]
Johnston-Peck A.C. et al., ACSNano 3 (5), 1077-1084 (2009)
[4]
Schmid M., et al., Physical Review Letters 99, 196104 (4p) (2007)
152
Complementary Study of ZnO nanorods by
Scanning Probe Microscopy
I. Beinik1, M. Kratzer1, G. Brauer2, W. Anwand3, X. Chen4, Y. F. Hsu4,
A.B. Djuriši4 and C. Teichert1
1
Institut für Physik, Montanuniversität Leoben, Austria, [email protected]
Institut für Ionenstrahlphysik und Materialforschung, Forschungszentrum DresdenRossendorf, Germany
3
Institut für Strahlenphysik, Forschungszentrum Dresden-Rossendorf, Germany
4
Department of Physics, University of Hong Kong, P.R. China
2
ZnO exhibits a wide spectrum of morphologies on the nano- and meso- scale [1]
which are of prospects to become functional [2,3]. Nanorods (NRs) made of ZnO
are of particular interest for application in UV photosensors [4] and solar cells [5].
Recently, ZnO NRs have been suggested for the conversion of mechanical to
electrical energy [6]. These applications require a detailed insight into the electrical,
opto-electrical, and electro-mechanical properties of the ZnO NRs. One of the most
appropriate tools to achieve this purpose is conductive atomic force microscopy (CAFM). C-AFM has been proven to be suitable in characterization of thin dielectric
films [7], low-dimensional semiconductor structures [8] and electroceramics [9]. The
opto-electrical and electro-mechanical properties of the NRs can be studied using
photoconductive AFM (PC-AFM) and piezoresponse force microscopy (PFM),
respectively.
Here, we present a C-AFM study of individual ZnO nanorods [10] grown by
hydrothermal synthesis [1,2] and thermal evaporation [3]. Both types of rods have
been grown on Si (100) and ITO substrates. Measurements were performed in air
and nitrogen atmosphere at variable temperatures. Current-voltage characterization
on individual upright standing nanorods revealed a characteristic similar to that of a
p-n diode. Along with the C-AFM studies, nanorods were also characterized by
means of PFM and PC-AFM. Detailed discussion of the opto- and piezo-electrical
properties is based on local I-V curves measured under- and without illumination, as
well as on the PFM images recorded from specific areas.
References
1.
L.E. Greene, et al., Nano Lett. 5, 1231 (2005).
2.
K.H. Tam, C.K. Cheung, Y.H. Leung, A.B. Djuriši, C.C. Ling, C.D. Beling,
S. Fung, W.M. Kwok, Y.H. Leung, W.K. Chan, D.L. Phillips, L. Ding, W.K.
Ge, J. Phys. Chem. B 110, 20865 (2006).
3.
Y.F. Hsu, Y.Y. Xi, A.B. Djuriši, W.K. Chan, Appl. Phys. Lett. 92, 133507
(2008).
4.
L. Luo, Y. Zhang, S. S. Mao and L. Lin, Sensors and Actuators A 127, 201
(2006).
5.
I. Gonzalez-Valls and M. Lira-Cantu, Energy Environ. Sci. 2, 19 (2009).
6.
Z.L. Wang, J. Song, Science 312, 242 (2006).
153
7.
8.
9.
10.
S. Kremmer, H. Wurmbauer, C. Teichert, G. Tallarida, S. Spiga, C. Wiemer
and M. Fanciulli, J. Appl. Phys. 97, 074315 (2005).
P. Tejedor, L. Díez-Merino, I. Beinik, C. Teichert, Appl. Phys. Lett. 95,
123103 (2009).
M. Schloffer, C. Teichert, P. Supancic, A. Andreev, Y. Hou, Z. Wang, J. Eur.
Cer. Soc 30, 1761 (2010).
G. Brauer, et al., Phys. Status Solidi C 6, 2556 (2009).
Tricking AFM to Its Limit
F. J. Schmied1,3, R. Schennach2,3 and C. Teichert1,3
1
Institute of Physics, University of Leoben, Franz Josef Str. 18, A 8700 Leoben
Institute of Solid State Physics, Graz University of Technology, Petersgasse 16/2,
8010 Graz
3
CD-Laboratory for Surface Chemical and Physical Fundamentals of Paper
Strength, Graz University of Technology, Petersgasse 16/2, 8010 Graz
2
Atomic Force Microscopy (AFM) is an appropriate tool to investigate structures on
the nanometer scale with various surface sensitive techniques, such as Conductive
AFM (CAFM), Friction Force Microscopy (FFM) and Phase Imaging which is based
on Tapping Mode AFM. These methods are well known and are standard
applications for AFM, especially the latter one.
Measurements on the micrometer scale are harder to access by AFM due to
restrictions of the piezo movement in xy-direction as well as for rough structures in
z-direction. Limitations of the applied force are based on the cantilever stiffness.
Usually, the cantilever stiffness for different AFM application ranges from 0.01 μN to
50 μN. In this work, a method is presented that deals with cantilever stiffness
between 300 to 400 μN. Limitations and solutions are presented to trick a
conventional AFM and push the system to its limit. First measurements of forces up
to allmost 1 mN are presented on single pulp fibers.
Supported by Mondi and the Christian Doppler Research Society, Vienna,
Austria.
E-mail of corresponding author: [email protected]
154
Structure and Phonon Dispersionof Bi(111) from He Atom Scattering
M. Mayrhofer-Reinhartshuber1, A Tamtögl1, W E Ernst1 and K H Rieder2
1
Institute of Experimental Physics, Graz University of Technology, Graz, Austria
Empa, Swiss Laboratories for Materials & Research, Zurich, Switzerland
2
As a material with significant differences in bulk and surface properties, bismuth (Bi)
has attracted renewed interest among researchers. The presence of metallic
surface states is unusual for a bulk semimetal and provides the playground for
ideas related to the electronic response of the surface and even the possibility of
two-dimensional superconductivity [1].
With regard to phonon states, calculations of the bulk phonon dispersion are
consistent with experimental data only when spin-orbit interaction is taken into
account [2]. Recently, squeezed bulk phonon states were measured with
femtosecond x-ray diffraction [3].
In contrast to phonons in the bulk and the electronic surface structure nothing is
known about the surface phonons of the Bi(111) surface. They are in a low energy
region of meV and therefore not accessible with satisfying resolution for most
scattering techniques, but with experiments using helium atom scattering (HAS)
surface phonons can be investigated successfully.
We have used elastic and inelastic HAS to study the Bi(111) surface therefore we
are able to present the first report on phonon creation and annihilation events on
this surface. The surface phonon dispersion relation has been determined from
measured time-of-flight spectra of inelastically scattered He atoms. The obtained
group velocity lies somewhat above the bulk group velocity. Elastic HAS
experiments reveal rather large diffraction peaks in comparison to other metals. A
first comparison between theoretical (eikonal approximation, GR-method) and
measured diffraction peak intensities yields a surface charge density corrugation of
16% of the surface unit cell. This value is surprisingly large since the reported
metallic character of the Bi(111) surface would imply a nearly flat corrugation. The
observed surface corrugation and the steep slope in the phonon dispersion may
both point to the important role of the strong covalent bonds at the surface.
References
[1]
Hofmann P 2006 Prog. Surf. Sci. 81 191
[2]
Díaz-Sánchez L E, Romero A H and Gonze X 2007 Phys. Rev. B 76 104302
[3]
Johnson S L et al. 2009 Phys. Rev. Lett. 102 175503
155
Trace Element Quantification in
High-Resolution Rutherford Backscattering Spectrometry
D. Primetzhofer*, and P. Bauer
Institut für Experimentalphysik, Johannes Kepler Universitaet Linz,
Rutherford backscattering spectrometry (RBS) is a versatile tool for analysis of
composition and thickness of nm-films. Low concentrations of heavy elements in
light matrices, e.g. transition metals in C, can easily be detected. In the present
work a multi-element organic compound, i.e. human blood was investigated to show
the potential of high-resolution RBS for quantification of trace elements. This is of
special interest also for other ion beam based techniques (e.g. SIMS, PIXE) have
been successfully applied for organic materials [1,2]
EXPERIMENT AND RESULTS
The experiments were performed employing the AN-700 accelerator at the
Johannes Kepler University of Linz, which can provide monoenergetic beams of
H,D and He ions with up to 700 keV primary energy. A high resolution LN2 cooled
surface barrier detector was used to record the spectra of backscattered projectiles
[3]. The blood sample was prepared in the following way: a droplet of human blood
was deposited on a graphite sample, dried in air and subsequently transferred to
the target chamber together with a graphite reference target.
Energy [keV]
100
110
120
130
140
150
160
170
180
190
200
210
220
230
240
Experiment
Simulated
C
N
O
Na
Mg
P
S
Cl
K
Ca
Fe
Zn
Se
Rb
10 000
Counts
1 000
100
10
1
50
55
60
65
70
75
80
85
90
95
100
105
110
115
120
125
Channel
Figure 1: RBS spectrum for 250 keV D+ scattered from a film of human blood deposited
on graphite. Shown are the experiment and a fit obtained by SIMNRA [4].
RBS spectra were recorded for 250 keV D+ ions scattered from the blood film and
the reference sample. Simulations of the RBS spectra were performed using the
program SIMNRA [4]. For the graphite reference target elements other than C were
below a concentration of 1.5 at%. From the shape of the RBS spectrum of the
156
organic sample it can be ascertained that the substrate signal is not visible. It was
possible to identify at least 10 chemical elements with high accuracy, as can be
seen in Fig.1. For instance, the concentration of Fe was determined to 350 +/- 10
ppm equivalent to 400 mg/L in perfect agreement with standard blood test values.
The detection limit for elements with atomic number higher than Fe is found to be
below 20 ppm. Note that it would be possible to resolve a concentration gradient
within the film by high-resolution RBS.
References
[1] A. Benninghoven, and W.K. Sichtermann, Analytical Chemistry 50 (1978) 1180
[2] R. Lobinski, C. Moulin, and R. Ortega, Biochimie 88 (2006) 1591
[3] M. Geretschläger, Nucl. Instr. and Meth. B 204 (1983) 479
[4] M. Mayer, Application of accelerators in research and industry 475 (1999) 541
Meyer-Neldel Rule and Disorder in Organic Devices
M. Ullah1, I. I. Fishchuk2, A. K. Kadashchuk3,4, A. Pivrikas5, P. Stadler5,
A. Kharchenko6, C. Simbruner1, N. S. Sariciftci5 and H.Sitter1
1
Institute of Semiconductor and Solid State Physics, JKU Linz, Austria.
Institute for Nuclear Research, National Academy of Sciences of Ukraine,
ProspectNauky 47,03680 Kyiv, Ukraine
3
IMEC, Kapeldreef 75, B-3001 Heverlee, Belgium
4
Institute of Physics, National Academy of Sciences of Ukraine,
Prospect Nauky 46,03028 Kyiv, Ukraine
5
Linz Institute of Organic solar cells, LIOS, JKU Linz, Austria.
6
PANalytical B.V., 7600 AA Almelo, The Netherlands
2
The performance of organic material based field effect transistors (OFETs) depends
on the field effect mobility which, now-a-days, approaches to 20 cm2 V1 s1 with
short molecules, and 0.2 cm2 V1 s1 with polymers. Fullerene “C60” is known as ntype organic semiconductor materials with its symmetric structure, low ionization
potential and high mobilities depending on different morphologies of C60 films (0.66cm2V-1s-1) [1-2]. In the present work we fabricated the OFETs using different
substrate temperature to grow different morphologies of C60 films by Hot Wall
Epitaxy system. Atomic Force Microscopy images and XRD results showed
increasing grain size with increasing substrate temperature. A shift in field effect
mobility was observed for different OFETs with different morphologies of C60 films
with increasing grain size. The temperature dependence of the field effect mobility
was determined in the accumulation regime of the device characteristics in the
temperature range from 300K to 80K. A change from an activated charge carrier
transport to a non-activated transport at lower temperatures was observed. The
temperature dependence of these devices showed different Arrhenius activation
157
energies. More over these C60 based OFETs follow the empirical relation between
the Arrhenius activation energy and the mobility prefactor named as Meyer-Neldel
Rule [2-3]. A shift in characteristic Meyer-Neldel energy, which can be described as
energetic disorder parameter of the material, was observed with changing C60 film
morphology [3]. As a consequence, the Meyer-Neldel energy can be considered as
material quality criterium, characterizing the width of energetic disorder [5]while the
carrier mobility depends on many other parameters not only on the degree of
disorder in the material.
References
[1]
Mujeeb Ullah, D. M. Taylor, R. Schwödiauer, H. Sitter, S. Bauer, N. S.
Sariciftci and Th. B. Singh, Journal of Applied Physics, 106, 114505 (2009).
[2]
Mujeeb Ullah, T.B. Singh, H. Sitter, N.S. Sariciftci, Applied Physics A,
Materials Science & Processing 97 (2009), 521.
[3]
Mujeeb Ullah, I. I. Fishchuk, A. Kadashchuk, P. Stadler, A. Pivrikas,
C. Simbrunner, V. N. Poroshin, N. S. Sariciftci, and H. Sitter, Appl. Phy. Lett.
96,213306 (2010).
[4]
I. I. Fishchuk, A. K. Kadashchuk, J. Genoe, Mujeeb Ullah, H. Sitter, Th. B.
Singh, N. S. Sariciftci, and H. Bässler, Phys. Rev. B 81, 045202 (2010).
[5]
A. Pivrikas, Mujeeb Ullah, Th. B. Singh, C. Simbrunner, G. Matt, H. Sitter
and N. S. Sariciftci, Organic Electronics submitted.
158
9. POSTER
9.1 AMP – Atome, Moleküle, Quantenphysik und Plasmen
POS-AMP-1
Hypergeometric Function Representation of Relativistic Transition
Matrix Elements for Hydrogenic Atoms and their Contributions
to the Lamb Shift
Nach Haupteingang links / Left of main entrance, Di, 7. Sept., 15:30 Uhr
1
2
1
G. Adam , A. V. Soldatov , J. Seke and M. Polak
1
1
lnstitut für Theoretische Physik, TU Wien, Wiedner Hauptstraße 8-10/136,
A 1040 Wien, Austria
[email protected]
2
V.A. Steklov Mathematical Institute, Dept. of Mechanics, 8, Gubkina str.
119991 Moscow, Russian Federation
[email protected]
By using the plane-wave expansion for the electromagnetic-field vector potential,
relativistic bound-bound, bound-unbound and unbound-unbound transition matrix
elements for hydrogenic atoms are expressed universally in terms of
hypergeometric functions of the type 2F1 in such a way that these functions only
depend on the absolute value of the wave vector |k| and the dependence on
angular variables of the wave vector is totally factored out and only comes through
functional multipliers built of spherical harmonics. By applying the obtained
formulae, these transition matrix elements can be evaluated analytically and
numerically with arbitrarily high precision. The newfound representation for the
matrix elements is very convenient for direct numerical evaluation of the Lamb shift,
especially at the second perturbational order, because its separable structure
allows for direct analytical integration over the angular variables of the wave vector
for the contribution to the shift from each matrix element, no matter bound-bound or
bound-unbound, thus resulting in only one one-dimensional integration to be
evaluated numerically. Universality, conciseness and strict reliance on functions,
already built in the standard computational packages contributes to making this
matrix elements representation preferable for programming of computationally
efficient algorithms in various QED-related problems.
Acknowledgements
This work was supported by the Dr. Anton Oelzelt-Newinsche Stiftung of the
Austrian Academy of Sciences, by the RAS research program “Mathematical
Problems of Nonlinear Dynamics” and by the RFBR grant No 09-01-00086-a.
159
POS-AMP-2
Investigation of Hyperfine Structures of Pr II Lines in the Region
572-579 nm by Collinear Laser Ion Beam Spectroscopy
N. Akhtar1, 2, H. Hühnermann1,3 and L. Windholz*, 1
1
Institute of Experimental Physics, Petersgasse 16, Technical University Graz,
Austria
2
Optics Labs P. O. Box 1021, Nilore Islamabad, Pakistan
3
Department of Physics, University of Marburg, Germany
* E-mail: [email protected]
In this work we have performed Doppler free hyperfine structure investigations of Pr
II, by the method of collinear laser ion beam spectroscopy. The hyperfine structure
(hfs) of a fine structure level is caused by electromagnetic interaction between
orbiting and spinning electrons and the nucleus. We have used praseodymium
powder in a surface ion source of Johnson type to produce praseodymium ions.
Due to the high density of low lying thermally populated metastable levels in
praseodymium, many transitions can be investigated. The ion beam is accelerated
to 20 kV and mass is separated by a 90° magnet. A collimated ion beam is obtained
in the light collection region. The excitation source is a ring dye laser pumped by an
Argon ion laser operated with Rhodamine 6G. In the interaction chamber, Doppler
tuning is carried out to investigate transitions in the region of 572 nm to 579 nm. A
photon counting method is used to record the laser induced fluorescence. Magnetic
dipole interaction constants A and the electric-quadrupole interaction constants B of
the involved levels have been determined using a fit program and the results are
found to be in good agreement with published values.
POS-AMP-3
Hyperfine Structure in the Line 5855 Å of 137Ba II Investigated by
Collinear Laser Ion Beam Spectroscopy
N. Akhtar1, 2, N. Anjum1, 2, H. Hühnermann1,3, C. Neureiter and L. Windholz* 1
1
Austria
2
Optics Labs P. O. Box 1021, Nilore Islamabad, Pakistan
3
* E-mail: [email protected]
160
The mass separator MARS-II, originally installed at the university of
Marburg/Germany, had been extensively used to investigate hyperfine structures
and isotopic shifts of different elements such as cesium, xenon, samarium,
promethium, lanthanum, barium, europium etc. This MARS-II system has been
transferred to Technical University Graz, in the Institute of Experimental physics
and is now producing first results. In a gas discharge, atom/ions have random
velocity distribution resulting in a Doppler broadened line shape. In collinear ion
beam spectroscopy, all ions have approximately uniform velocity; therefore a nearly
Doppler free spectrum is obtained.
Barium is used to calibrate the system. The ions were produced from Barium Nitrate
in a Johnson type surface ion source. These ions are accelerated to 20 kV and
then, a mass separator magnet separates different barium isotopes. Singly ionized
barium has two low lying metastable d-levels which are populated during the
production of ions. In the interaction chamber, Doppler tuning is carried out to
2
2
investigate the transition between 5d D3/2 o 6p P°3/2. A ring dye laser pumped by
an Argon ion laser is used as excitation source in the spectral range of Rhodamine
6G. Detecting the laser induced fluorescence by a photon counting method a well
resolved hyperfine structure of ionized barium-137 has been observed. The
recorded hyperfine structure is fitted using a fit program and the magnetic dipole
interaction constant A and the electric-quadrupole interaction constant B of the
combining levels are determined. The A, B values are found to be in good
agreement with the literature values.
POS-AMP-4
Measurements of Hyperfine Structure Constants of Pr II by Using High
Resolution Collinear Laser Ion Beam Spectroscopy
N. Anjum1, 2, N. Akhtar1, 2, H. Hühnermann1,3 and L. Windholz*,1
1
Austria
2
Optics Labs. P. O. Box 1021, Nilore Islamabad, Pakistan
3
*E-mail: [email protected]
We have used collinear laser ion beam spectroscopy (CLIBS) for Doppler free
investigations of hyperfine structure (hfs) of Praseodymium ions (Pr II). Due to
velocity bunching effect and selective excitation process CLIBS is a very powerful
technique for the precision study of hfs. Hyperfine structure is caused by the
electromagnetic interaction between the nucleus and orbital electrons. The study of
hyperfine structure of ions can provide useful information on the nuclear structure
and electronic properties of the ions.
In our experiment Pr ions are produced using a surface ion source of Johnson type.
Due to the high density of low lying thermally populated metastable levels in Pr II,
161
many transitions can be investigated. The ions are accelerated to 20 kV and then
mass separated by a 90° magnet. A collimated ion beam is obtained in the
interaction region. In the interaction region ions velocity is tuned by applying an
additional voltage and keeping the laser frequency constant (Doppler tuning) for the
investigations of spectral lines in the region of 5762 Å to 5841 Å. A ring dye laser,
pumped by an Argon ion laser, is used as the excitation source and we used dye
Rhodamine 6G to obtain the desired laser wavelengths. Laser induced fluorescence
is recorded by using a photomultiplier tube and a photon counter. Magnetic dipole
constants A and electric quadrupole constants B of the involved levels have been
determined using a fit program. Our results are in good agreement with published
values.
POS-AMP-5
Experimental Confirmation of a Universally Valid Uncertainty
Relation for Error and Disturbance in Spin-Measurements
J. Erhart*, S. Sponar*, G. Sulyok*, G. Badurek*, M. Ozawa†, and Y. Hasegawa*
*Atominstitut, Technische Universität Wien, Stadionallee 2, A-1020 Wien, Austria
†Graduate School of Information Science, Nagoya University, Nagoya 464-8601,
Japan
The uncertainty principle, which prohibits presice measurments of certain pairs of
quantum mechanical observa bles, is one of the most remarkable consequences of
quantum mechanics. It is well-known that Heisenberg, using the famous gamma-ray
microscope thought-experiment [1], suggested a trade-off relation where the
product of the measurement error of an observable and the disturbance on another
observable caused by the measurement is not less than a bound set by the
commutator between these two observables. Recently, Ozawa reconsidered this
relation between the error and the disturbance by rigourous and general theoretical
treatment of quantum measurements and derived the new relation,
(A) (B)+ (A) (B) + (A) (B) ½ |<|[A,B]|>|
where HKV are the error of the measurement A, the disturbance on the
measurement B, and the standard deviations, respectively. In this talk, we report a
neutron optical experiment that measures the error of a spin-component
measurement as well as the disturbance caused on another spin-component
measurement. This experiment confirms that the trade-off between the error and
the disturbance completely obeys the new relation but violates the old one in a wide
range of an experimental control parameter. Our results are the first evidence of the
solution of a long-standing problem to describe the relation between the
measurement accuracy and the disturbance caused by that measurement.
162
References
[1] Heisenberg, W. Über den anschaulichen Inhalt der quantentheoretischen
Kinematik und Machanik, Z. Phys. 43, 172 (1927).
[2] Ozawa, M. Universally valid reformulation of the Heisenberg uncertainty principle
on noise and disturbance in measurements, Phys. Rev. A 67, 042105 (2003).
[3] Ozawa, M. Uncertainty relations for noise and disturbance in generalized
quantum measurements, Ann. Phys. 311, 350 (2004).
POS-AMP-6
Spin Ensembles on a Chip: Collective Effects in Cavity QED
K. Henschel 1*, J. Majer 2, J. Schmiedmayer2 and H. Ritsch1
1
Institute for Theoretical Physics, Universität Innsbruck, Technikerstrasse 25,
A 6020 Innsbruck, Austria
2
Atominstitut, TU Wien, Stadionallee 2, A 1020 Vienna, Austria
*
Recipient of a DOC-fFORTE-fellowship of the Austrian Academy of Sciences
We study the dynamics of an ensemble of spins (two-level systems) coupled to a
resonant microwave cavity mode. The ensemble can consist in a cloud of ultracold
atoms or Nitrogen-Vacancy (NV) centers in a diamond. Despite the minute single
spin coupling one obtains strong coupling between collective states and microwave
photons enabling coherent transfer of an excitation between the long lived
ensemble qubit state and the mode. Evidence of strong coupling can be obtained
from the cavity transmission spectrum even at finite thermal photon number. In the
case of NV centers additional line broadening due to remaining (not converted)
Nitrogen in the crystal and NV-NV interactions have to be taken into account.
POS-AMP-7
Experimental Study on Optical Breakdown Induced by
Polychromatic Laser Radiation
A. Kremsner, G. Reider, E. Schwarz, E. Wintner
Photonics Institute, Vienna University of Technology,
Gusshausstrasse 25-29, 1040 Wien, Austria
Phone: +43 (1) 58801-38715
E-mail: [email protected] ,
Phone: +43 (1) 58801-38788
Phone: +43 (1) 58801-38727
Phone: +43 (1) 58801-38712
163
We present experimental results concerning coherence effects in two color laser
plasma generation in air at atmospheric pressure. Furthermore this experiment was
also achieved at elevated pressures up to 10 bar.
In order to obtain two-color radiation, second harmonic generation (SHG) can be
employed. Therefore a commercial Q-switched 1064 nm Nd:YAG laser (Quantel
Brilliant, pulse length 5 ns, maximum energy 250 mJ) was frequency-doubled via a
KDP crystal.
To obtain an overlap of the foci of the two wavelengths 1064 nm and 532 nm, a
curved mirror with a HR coating for both wavelengths was used.
These experiments have been conducted to optimize a laser ignition system for gas
engines, which was developed by the “Laser Ignition Group” [1,2] at the “Institut für
Photonik”. The outcome was a compact high peak power, passively Q-switched,
longitudinally diode-pumped solid-state laser. One day this “laser spark plug” should
replace conventional spark plugs because of the fact that conventional ignition has
reached its limit in terms of efficiency and reduction of pollutant emissions.
References
[1]
H. Kopecek, E. Wintner, M. Lackner, F. Winter, and A. Hultqvist, LaserStimulated Ignition in a Homogeneous Charge Compression Ignition
Engine. SAE SP. 1819, 183 (2004).
[2]
H. Kofler, J. Tauer, G. Tartar, K. Iskra, J. Klausner, G. Herdin, and E.
Wintner, An Innovative solid-state laser for engine ignition. Laser Physics
Letters. 4(4), 322 (2006).
POS-AMP-8
Implementation of a High-Power Frequency-Doubled Laser System for
the Generation of an Optical Superlattice
L. Reichsöllner1, J. Danzl1, M. Mark1, E. Haller1, R. Hart1, A. Klinger1,
O. Krieglsteiner1 and H.-C. Naegerl1
1
Institut fuer Experimentalphysik und Zentrum fuer Quantenphysik, Universität
Innsbruck, Technikerstraße 25/4, 6020 Innsbruck, Austria;
E-mail of presenting author: [email protected]
Bose-Einstein condensates loaded into optical lattice potentials allow the realization
of model Hamiltonians with exquisite control over the experimental parameters.
Superimposing an optical lattice potential with a second lattice featuring exactly half
the lattice spacing allows to generate a so called superlattice that features a tunable
double-well configuration.
We implement the fundamental lattice at a wavelength of 1064 nm and generate
light at 532 nm for the short lattice by first power amplifying the 1064 nm light and
subsequently frequency doubling it. For cesium atoms, the light for the fundamental
164
lattice is red detuned with respect to the atomic transition, whereas the lattice at 532
nm is blue detuned and hence creates a repulsive potential.
The superlattice will allow the investigation of novel quantum phases in optical
lattices with complex occupation patterns and optimized formation of doubly
occupied lattice sites for ultracold molecule production.
POS-AMP-9
Anomalous Intensity Distribution of Hyperfine Components
of Praseodymium-I Lines
I. Siddiqui, G. Guthöhrlein and L. Windholz
Institut für Experimentalphysik, Techn. Univ. Graz, A-8010 Graz, Petersgasse 16
[email protected]
Experimental investigation of praseodymium-I line at wavelength 578.051 nm is
reported. This investigation led to the observation of a laser induced fluorescence
signal at 618.3 nm. The subsequently recorded hyperfine structure of the line
showed an anomalous intensity distribution of its hyperfine components. The
unusual intensity of hyperfine components was observed not only at 618.3 nm but
also on other fluorescence lines i.e. 337.284 nm, 482.014 nm, 483.607 nm, 520.515
nm. Three groups of closely spaced hyperfine patterns are clearly seen and we
concluded that three transitions are always excited. These closely spaced levels
could disturb each other, explaining also the quite unusual intensity distribution of
the hyperfine patterns. From the analysis of the wave numbers of the observed
fluorescence lines we were able to determine the upper level of the excited
transition at a wave number of 32486.80 cm-1, with J = 15/2 and even parity.
Excitation with wavelength 618.3 nm confirmed our assumptions concerning energy
and J of this upper level without doubt; its A-factor was 552.5 MHz. Thus we were
able to locate three closely spaced levels with center-of-gravity distances 0.18 cm-1
and 0.68 cm-1 respectively as lower levels of the excited transitions. Up till now we
have made 54 excitations from these narrow spaced levels to different known or
unknown upper levels. In all these excitations an anomalous intensity distribution of
hyperfine components is observed.
These levels are
15192.090 cm-1, J = 15/2, A = 730 MHz, odd parity
165
POS-AMP-10
Experimental Investigation of Hyperfine Structure of
Praseodymium-I Lines: Discovery of New Fine Structure Levels
in Even and Odd Configurations
K. Shamim and l. Windholz
Institut für Experimentalphysik, Techn. Univ. Graz, A-8010 Graz, Petersgasse 16
[email protected]
We report here the experimental investigation of the hyperfine structure of
praseodymium-I lines using laser induced fluorescence spectroscopy in a hollow
cathode discharge lamp. In this work 150 spectral lines were investigated which
resulted in the discovery of 30 low lying new, up to now unknown levels, both in
even and odd configurations. From the experimentally recorded data, using lock-in
detection technique, magnetic hyperfine interaction constant ‘A’ and angular
momentum ‘J’ were evaluated. With the help of the determined angular momentum
‘J’ and hyperfine interaction constant ‘A’, one of the involved levels is identified and
the energy of the second new level is determined by the addition of the excitation
wave number. The level found in this way explains fluorescence wavelengths and
hyperfine structure of the fluorescence lines appearing in FT-Spectra. The newly
discovered levels are further confirmed experimentally by excitations from other
known lower levels.
POS-AMP-11
New Odd Parity Levels in Neutral Praseodymium
S. Tanweer I., and L. Windholz*
Institut für Experimentalphysik, Techn. Univ. Graz, A-8010 Graz,
Petersgasse 16, Austria
*Email: [email protected]
The spin-orbit interaction is the largest relativistic effect and is responsible for fine
structure splitting in an atom. The hyperfine splitting of fine structure levels arise
due to the interaction between electromagnetic multipole nuclear moments and the
electromagnetic field produced at the nucleus by the electrons. In this investigation
of the hyperfine structure of the praseodymium atom, presenting the discovery of
thirteen newly found odd parity levels by investigation of spectral lines in the region
5640 Å to 6900 Å. In a hollow cathode discharge through the process of sputtering
praseodymium atoms and ions are produced in ground and excited states which are
then further excited to higher states by laser light. The excitation sources are
operated with R6G or Kiton red ring-dye laser pumped by a solid state diodepumped, frequency doubled Nd:Vanadate Nd:YVO4 Verdi V-18 laser system The
166
hyperfine structure of these transitions has been recorded by using the method of
laser induced fluorescence.
J-quantum numbers and magnetic dipole interaction constant A-values for
upper and lower levels have been determined from the recorded hyperfine
structure. The energies of the new up to now unknown levels have been obtained
by using these constants, excitation and fluorescence wavelengths. The excitation
wavelengths have been taken from FT Spectra [1]. Levels confirmed by a second
laser excitation are given in the following table.
Excitation Wavelength Signal/Noise in FT Spectra Discovered Odd Levels
Å
J
Energy/ cm1
1
5757.311
7
15/2
32784.550
2
6057.921
17
9/2
28215.962
3
6161.912
3
5/2
27870.498
9/2
4
5784.751
19
23817.624
11/2
5
5771.459
5
31650.077
6
6789.737
3
5/2
26593.377
7
6596.887
4
17/2
27405.078
8
6207.232
21
9/2
22641.371
9
6142.813
3
17/2
32925.303
10
5664.825
3
17/2
35343.038
11
5726.241
6
17/2
33124.449
12
5740.394
7
11/2
30688.196
13
5911.494
7
5/2
31789.369
1. B. Gamper, Diploma Thesis, Technical University of Graz, 2007 (Unpublished)
167
9.2 FAKT – Fachausschuss Kern- und Teilchenphysik
POS-FAKT-1
Design of a 1.42 GHz Spin-Flip Cavity for Antihydrogen Atoms
S. Federmann1,2, F. Caspers1, E. Mahner1, B. Juhasz2 and E. Widmann2
1
CERN, Geneva, Switzerland
Stefan Meyer Institute for Subatomic Physics, Vienna, Austria
2
The ground state hyperfine transition frequency of hydrogen is known to a very high
precision and therefore the measurement of this transition frequency in
antihydrogen is offering one of the most accurate tests of CPT symmetry.
The ASACUSA collaboration at CERN will run an experiment designed to produce
ground state antihydrogen atoms in a cusp trap. These antihydrogen atoms will
pass with a low rate in the order of one per second through a spin-flip cavity where
they get excited depending on their polarization by a 1.42 GHz magnetic field.
Due to the small amount of antihydrogen atoms that will be available the
requirement of good field homogeneity is imposed in order to obtain an interaction
with as many antihydrogen atoms as possible. This leads to a requirement of an RF
field deviation of less than ± 10% transverse to the beam direction over a beam
aperture with 10 cm diameter.
All design aspects of this new spin-flip cavity, including the required field
homogeneity and vacuum aspects, are discussed.
References
[1]
B. Juhasz, E.Widmann, Hyp. Int. 193 (2009) 305
[2]
N.F. Ramsey: Nobel Lecture (1989)
[3]
M. Shibata, A. Mohri, Y. Kanai, Y. Enomoto, Y. Yamazaki: Compact
cryogenic system with mechanical cryocoolers for antihydrogen synthesis,
Review of Scientific Instruments 79, 015112 (2008)
[4]
T. Kroyer: Design of a Spin-Flip Cavity for the Measurement of the
Antihydrogen Hyperfine Structure, CERN-AB-Note, 2008
POS-FAKT-2
Readout Electronics for the Belle II Silicon Vertex Detector
C. Irmler1, T. Bergauer1, M. Friedl1, I. Gfall1, M. Valentan1
1
Institute of High Energy Physics, Nikolsdorfergasse 18, A-1050 Vienna, Austria
[email protected]
A major upgrade of the KEK-B factory (Tsukuba, Japan), aiming at a peak
luminosity of 8 x 10^35 / (cm^2s), which is 40 times the present value, is foreseen
168
until 2013. Consequently an upgrade of the Belle detector and in particular its
Silicon Vertex Detector (SVD) is required.
The new Belle II SVD will consist of four layers of double-sided silicon strip
sensors at radii of 3.8, 8, 11.5 and 14 cm, completed by a double-layer pixel
detector as the innermost sensing device. All DSSDs will be read out by the APV25
chip, which was originally developed for the CMS experiment. It has a peaking time
of nominally 50ns, an integrated analog pipeline of 192 cells and has been proven
to meet the requirements for Belle II in matters of occupancy and dead time. Since
the KEK B-factory operates at relatively low energy, material budget inside the
active volume has to be kept low to minimize multiple scattering.
We will present the concept of the readout electronics of the future Belle II
SVD. Its front-end uses the APV25 readout chip arranged according to the Origami
chip-on-sensor concept to ensure both low material budget and lowest possible
amplifier noise. The VME back-end system not only digitizes the analog signals, but
also provides on-board data processing and sparsification. It further allows
determining exact hit timing with a precision of a few nanoseconds by taking six
consecutive samples of the APV shaper output signal. Thanks to this feature, hits
from background particles can be identified and discarded, which finally leads to a
significant occupancy reduction. Even though the development of the readout
electronics is still ongoing, we have successfully tested its building blocks on
prototypes in several beam tests and the lab.
In 2009, the principal feasibility of the Origami concept [1] has been shown
by building a prototype module using a 4" DSSD. Recently, new Belle II sensors
(6") were delivered, and we are now assembling an Origami module for this full size
sensor. Later this year, we want to build a full ladder of the outermost layer, as this
will be the most complicated object and by demonstrating its producibility we thus
prove the concept of the whole Belle II SVD. Starting from the assembly steps of
the 2009 prototype, we will further elaborate and refine the procedure, aiming at a
mechanical precision in the order of few 10um.
References
[1]
C. Irmler et al.,”Construction and Performance of a Double-Sided Silicon
Detector Module Using the Origami Concept”, CERN-2009-006, 211-215
(2009)
POS-FAKT-3
Quench Prevention of the LHC Quadrupole Magnets
C. Kurfürst1, B. Dehning2, C. W. Fabjan3, E. B. Holzer4,
A. Nordt5 and M. Sapinski6
1
865/1-C09, CERN, 1211 Geneva, Switzerland, [email protected],
865/1-C05, CERN, 1211 Geneva, Switzerland,
3
Institute of High Energy Physics, Nikolsdorferg. 18, 1050 Vienna, Austria.
2, 4, 5, 6
CERNs Large Hadron Collider (LHC) is a high energy proton accelerator and
storage ring. Its design allows to reach unprecedented beam energies and beam
169
intensities, resulting in a largely increased particle physics discovery potential. The
combination of its high beam energy and intensity may lead to beam losses which
can have a severe impact on the LHC equipment and damage sensitive elements.
To protect those and to measure operational losses, a Beam Loss Monitoring (BLM)
system has been installed all along the ring. The protection is achieved by
extracting the beam from the ring in case thresholds imposed on measured
radiation levels are exceeded.
The thresholds are estimated through particle shower simulations. The simulated
geometry and physic processes need to be precise in order to determine an
optimum value, which therefore assures a high availability of the LHC for operation.
This study is focused on the interconnection region between the main dipole and
the main quadrupole magnet of the LHC. Six monitors are placed around the
interconnection, three for each beam line. As proton impact location two loss
patterns are assumed: one derived from halo particle tracking simulations and the
other through analytic calculations relying on optical beam parameters.
Particle shower simulations make the link between the amount of energy deposited
in the superconducting coil and the signal measured in the ionisation chambers.
The energy deposition in the coil results in its temperature increase. In case a
critical temperature is exceeded, a transition from the superconducting state to the
normal conducting one will occur. This transition is called a quench and is analysed
for steady state and for fast transient losses. The fundamental parameters for the
analysis are the critical power density and the enthalpy margin respectively.
The combination of the detector signals allows the reconstruction of the loss
pattern. Also the quench-protecting thresholds for two protection schemes have
been evaluated.
First LHC results are used to verify the simulations and considerations with
measurements, so that conclusions about the simulation accuracy and observed
loss patterns could be drawn.
For transient losses the quench protecting threshold used as initial setting in the
BLM system for the 2010 run is for the first ionisation chamber of 1520 μGy at
injection energy and 178 μGy at 7 TeV beam energy. For steady state losses the
used threshold for the first ionisation chamber is 4960 μGy/s at injection energy and
1876 μGy/s at collision energy.
POS-FAKT-4
The Federated Tier-2 Computing Center for LHC
D. Liko1,a, D. Kuhn2, N. Hörman1, G. Mair2 and W. Jais2
1
Institute for High Energy Physics, Austrian Academy of Sciences, Vienna
Institute for Astro and Particle Physics, University of Innsbruck
a
[email protected]
2
The Worldwide LHC Computing Grid project (WLCG) [1] has established a global
computing infrastructure for the analysis of LHC data [2]. It is based on several
170
large grid projects, the EGEE project in Europe [3] and the Open Science Grid
(OSG) in the US [4]. With the start of LHC a new international structure has been
established in Europe, the European Grid Initiative (EGI) [5], to provide a
sustainable
support
for
the
infrastructure
in
the
coming
years.
In Austria, supported by the BMWF, the AustrianGrid project [6] has also
established a federated Tier-2 centre for LHC with large computing clusters in
Vienna and Innsbruck. It builds the basis for the LHC data analysis of the Austrian
particle physics community. The Tier-2 is again supported by an Austrian National
Grid Initiative (NGT_AT) that integrates into the European structure. With the start
of the collider operation also the Austrian part of the grid has demonstrated its
capabilities and data from the ATLAS and the CMS experiment are being analysed
in Austria from the first day. As of today a number of other research areas, as
biology, radio-biology and theoretical physics are also profiting from the available
resources.
References
[1]
Worldwide LHC Computing Grid (WLCG), http://cern.ch/lcg,
Memorandum of Understanding, (CERN-C-RRB-2005-01/rev.), 2009.
[2]
The LCG Editorial Board, ”LHC Computing Grid Design Report”, LCG-TDR001 (CERN-LHCC-2005-024), 2005.
[3]
Enabeling Grids for E-SciencE (EGEE), http://www.eu-egee.org/,
FP7 Project INFSO-RI-222667
[4]
Open Science Grid, http://www.opensciencegrid.org/
[5]
European Grid Initiativehttp://www.egi.eu/,
EGI Bluprint, EU Deliverable D5.3, http://www.eu-egi.eu/blueprint.pd
[6]
Austrian Grid Project, http://www.austriangrid.at,
Austrian Grid is a project funded by the BMWF (Federal Ministry of Science and
Research). Contract: GZ BMWF-10.220/0002-II/10/2007
POS-FAKT-5
Bound-State Stability in Bethe–Salpeter Equations with
Instantaneous Confinement
W. Lucha
Institute for High Energy Physics, Austrian Academy of Sciences,
Nikolsdorfergasse 18, A-1050 Vienna, Austria
Instantaneous Bethe–Salpeter equations with - supposedly - confining interaction
kernels are expected to predict stable bound states with associated mass
eigenvalues belonging to a part of the resulting total mass spectrum that is real,
discrete and — preferably — bounded from below. Basically numerical studies,
171
however, reveal that this requirement is not automatically satisfied. Hence, it has to
be established in each individual case that for a chosen Lorentz structure of the
kernel all desired spectral features are indeed achieved. Assuming the confining
potentials to be of harmonic-oscillator form in configuration space greatly simplifies
this kind of spectral analysis.
References
[1]
W. Lucha and F. F. Schöberl, “Instantaneous Bethe–Salpeter Equation with
Exact Propagators”, J. Phys. G: Nucl. Part. Phys. 31, 1133 (2005)
[2]
Li Z.-F., W. Lucha, and F. F. Schöberl, “Exact-Propagator Instantaneous
Bethe–Salpeter Equation for Quark–Antiquark Bound States”, Mod. Phys.
Lett. A 21, 1657 (2006)
[3]
Z.-F. Li, W. Lucha, and F. F. Schöberl, “Stability in the Instantaneous Bethe–
Salpeter Formalism: Harmonic-Oscillator Reduced Salpeter Equation”, Phys.
Rev. D 76, 125028 (2007)
[4]
Z.-F. Li, W. Lucha, and F. F. Schöberl, “Stability in the Instantaneous Bethe–
Salpeter Formalism: Reduced Exact-Propagator Bound-State Equation with
Harmonic Interaction”, J. Phys. G: Nucl. Part. Phys. 35, 115002 (2008)
POS-FAKT-6
Quark–Hadron Duality and Effective Continuum Thresholds in
Dispersive Sum Rules
W. Lucha1, D. Melikhov2,3,4 and S. Simula5
1
Institute for High Energy Physics, Austrian Academy of Sciences,
Nikolsdorfergasse 18, A-1050 Vienna, Austria
2
Institute for High Energy Physics, Austrian Academy of Sciences, Vienna, Austria
3
Faculty of Physics, University of Vienna, Austria
4
SINP, Moscow State University, Russia
5
INFN, Sezione di Roma III, Roma, Italy
We consider the extraction of ground-state parameters within the framework of
QCD sum rules, with emphasis on the crucial ingredient of this approach, viz., the
effective continuum threshold, which governs the accuracy of the duality
approximation. We propose a new algorithm to fix this quantity and probe both
reliability and actual accuracy of sum-rule predictions at the example of quantummechanical potential models, which allow for comparison with the exact solutions.
Our procedure yields a significant improvement of the accuracy of resulting groundstate parameters compared with standard sum-rule techniques used in all previous
applications of dispersive sum rules in QCD. Moreover, the procedures of extracting
ground-state decay constants in potential models and in QCD prove to be
quantitatively very similar. Thus, the application of the proposed algorithm in QCD
172
promises to result in a considerable increase of the accuracy of the extracted
hadron parameters.
References
[1]
W. Lucha, D. Melikhov, and S. Simula, “Effective Continuum Threshold in
Dispersive Sum Rules”, Phys. Rev. D 79, 096011 (2009)
[2]
W. Lucha, D. Melikhov, and S. Simula, “Bound-State Parameters from
Dispersive Sum Rules for Vacuum-to-Vacuum Correlators“, J. Phys. G: Nucl.
Part. Phys. 37, 035003 (2010)
[3]
W. Lucha, D. Melikhov, H. Sazdjian, and S. Simula, “Effective Continuum
Threshold for Vacuum-to-Bound-State Correlators”, Phys. Rev. D 80,
114028 (2009)
[4]
W. Lucha, D. Melikhov, and S. Simula, “Extraction of Ground-State Decay
Constant from Dispersive Sum Rules: QCD vs. Potential Models“, Phys. Lett.
B 687, 48 (2010)
[5]
W. Lucha, D. Melikhov, and S. Simula, “Extraction of Bound-State
Parameters from Dispersive Sum Rules“, arXiv:1003.1463 [hep-ph], Phys.
Atom. Nucl. 73 (2010) (in print)
POS-FAKT-7
Recent Advances in AMS of 36Cl with a 3-MV-Tandem
M. Martschini1,*, O. Forstner1, R. Golser1, W. Kutschera1, S. Pavetich1,
A. Priller1, P. Steier1, M. Suter2 and A. Wallner1
1
VERA Laboratory, Fakultät für Physik - Isotopenforschung, Universität Wien,
Währingerstraße 17, A-1090 Wien, Austria; *[email protected]
2
Ion Beam Physics, Department of Physics, ETH Zürich, Schafmattstraße 20,
CH-8093 Zürich, Switzerland
36
Cl (t1/2 = 0.30 Ma) is widely used for exposure dating of carbonate rocks such as
limestone and calcite. Accelerator mass spectrometry (AMS) with its high sensitivity
allows to measure 36Cl at natural isotopic concentrations (36Cl/Cl ~ 10-13) but
requires high particle energies for the separation from the stable isobar 36S. At
VERA (Vienna Environmental Research Accelerator) we had performed the first
36
Cl exposure dating measurement with a 3-MV tandem accelerator, operating our
machine at 3.5 MV, using foil stripping and a split-anode ionization chamber [1].
We evaluated the performance of various detectors for 36Cl [2]. With the ionization
chamber and a residual energy signal from a silicon strip detector, we now achieved
an equally good 36S suppression at 3 MV terminal voltage compared to 3.5 MV in
our previous measurements. To further increase the 36S suppression we
investigated energy loss straggling in various counting gases and the effect of
“energy focusing” [3] below the maximum of the Bragg curve. Comparison of
experimental data with simulations and published data [3,4] yielded interesting
173
insight into the physics underlying the detectors. Energy loss, energy straggling and
angular scattering determine the 36S suppression.
In addition, we improved ion source conditions, target backing materials and the
cathode design with respect to sulfur output and cross contamination. These
changes allow higher currents during measurement (35Cl current | 5 A) and also
increased the reproducibility. We achieve an injector to detector efficiency for 36Cl
ions of 8% (16% stripping yield for the 7+ charge state in the accelerator, 50% 36Cl
detection efficiency), which compares favorable to other facilities. We will
demonstrate that 36Cl measurements, which are competitive to larger tandems, are
now possible.
References
[1]
P. Steier, O. Forstner, R. Golser, W. Kutschera, M. Martschini, S. Merchel,
T. Orlowski, A. Priller, C. Vockenhuber, A. Wallner, Nucl. Instr. Methods
Phys. Res. B 268 (2010) 744
[2]
T. Orlowski, O. Forstner, R. Golser, W. Kutschera, M. Martschini, S.
Merchel, A. Priller, P. Steier, C. Vockenhuber, A. Wallner, Nucl. Instr.
Methods Phys. Res. B 268 (2010) 847
[3]
H. Schmidt-Böcking, H. Hornung, Z. Physik A286 (1978) 253
[4]
L.C. Northcliffe, R.F. Schilling, Nucl. Data Tabl. A7 (1970) 233
POS-FAKT-8
Developments Towards Radiocarbon Dating
of Ultra-Small DNA Samples
K. Mair, J. Liebl , P. Steier and W. Kutschera
Vienna Environmental Research Accelerator (VERA) Laboratory,Fakultät für Physik
– Isotopenforschung, Universität Wien, Währingerstrasse 17, A-1090 Wien, Austria
Radiocarbon (14C) dating using Accelerator Mass Spectrometry (AMS) is a well
established method. Standard methods of AMS typically require a sample size
of about one milligram carbon, which, however, is not available in our recent
efforts towards dating DNA from small human brain tissue samples using the
14
C bomb peak [1]. We are presently developing methods to reliably measure
samples in the range of ~10 Pg C. In decreasing the sample size, the main
challenge is the control of the laboratory background which typically stays
constant, and finally dominates the measurement result. In order to keep carbon
contamination at the lowest possible level, an argon atmosphere – instead of air
- was provided in sample handling, sample preparation, and ion source loading.
Most of these tasks were performed in an argon glove box.
Since we couldn’t find a significant difference in the carbon background for the
ultra-small samples between sample preparation in laboratory air and argon
atmosphere, we tested our argon-controlled set-up with mg-size samples of
14
geological graphite (nominally zero C content), and found a radiocarbon age
174
of 77 000 years BP. This is the lowest 14C background we have measured at
VERA so far. It corresponds to a fraction modern carbon (F14C) value of (6.3 ±
1.4)x10-5. This is about one 14C half life "older" than samples processed in
laboratory atmosphere. However, It was not possible to measure such a low
value with ~10 μg graphitized carbon samples, because contamination from
other sources seems to dominate the overall background.
In a different investigation, we studied the mass of carbon contamination
incorporated during different steps of sample preparation using small samples
highly enriched in 13C. The amount of contamination with normal carbon (99%
12
C) present in CO2 from sample combustion can be assessed by measuring
13
CO2/12CO2 ratios using an RGA (residual gas analyzer). Additional
contamination from the graphitization process was determined by measuring
13
C/12C ratios with AMS. An overall amount of 0.12 to 0.15 Pg C contamination
was found in this way [2].
References
[1]
Spalding, K. L., Bhardwaj, R. D., Buchholz, B. A., Druid, H., Frisen,
J., “Retrospective birth dating of cells in humans”, Cell 122, 133-143
(2005).
[2]
Liebl, J., Avalos Ortiz, R., Golser, R., Handle, F., Kutschera, W., Steier,
P., Wild, E. M., “Studies on the preparation of small 14C samples with an
RGA and 13C enriched material”, accepted for publication in Radiocarbon.
POS-FAKT-9
Gem Detector Development for Hadron-Physics Experiments
P.Müllner1,a and J. Zmeskal1
1
Stefan Meyer Institut für subatomare Physik
a
[email protected]
The next experiments in hadron-physics aim at studying rare processes with
improved sensitivity (e.g. PANDA) [1]. The technical requirements for these
experiments include fast detectors for charged particles with large acceptance and
excellent tracking capabilities. With the GEM (Gas Electron Multiplier) technology it
is possible to build detectors, which meet the demands for such experiments.
The GEM technology bases on a thin polymide foil with a copper cladding on both
sides [2]. A large number of microholes are chemically etched into this foil. By
applying a voltage difference of several hundred volts, an electrical field of several
kV/cm is produced inside the holes. Therefore the holes acts as a multiplication
channel for electrons and as a trap for positive charged particles. A GEM detector is
a gas detector with one or more GEM foils mounted between the cathode and
anode.
175
The SMI (Stefan Meyer Institute for subatomic physics) in Vienna build a triple GEM
detector with an active area of 50x50 mm2, which was tested with PIXE (Proton
Induced X-ray Emission) at the VERA (Vienna Environmental Research
Accelerator). The location dependence of the intrinsic efficiency across the
detection area was examined. Due to the collected experience from the results of
these test, the SMI build now a new triple GEM detector prototype with a larger
active area of 100x100 mm2 and improved readout electronics.
References
[1]
Schmitt, L., “The PANDA detector at FAIR”, Nuclear Instruments and
Methods in Physics Research A 581, 542-544 (2007)
[2]
Sauli, F., “GEM: A new concept for electron amplification in gas detectors”,
Nuclear Instruments and Methods in Physics Research A 386, 531-534
(1997)
POS-FAKT-10
AMS Measurement of the Reaction 35Cl(n,J)36Cl and its Relevance
to Astrophysics and Nuclear Technology
S. Pavetich1, T. Belgya2, M. Bichler3, I. Dillmann4, O. Forstner1, R. Golser1,
F. Käppeler4, Z. Kis2, M. Martschini1, A. Priller1, P. Steier1, G. Steinhauser3,
2
1
L. Szentmiklosi and A. Wallner
1
VERA Laboratory, Faculty of Physics, University of Vienna, Währinger Str. 17,
1090 Vienna, Austria, [email protected]
2
Department of Nuclear Research, Institute of Isotopes, Hungarian Academy of
Sciences, 1525 Budapest, Hungary
3
Atominstitut der Österreichischen Universitäten (ATI), Stadionallee 2, 1020
Vienna, Austria
4
Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe,
Germany
36
Cl is a long-lived radionuclide (t1/2 = 301000 a), which is dominantly produced via
the reaction 35Cl(n,J)36Cl. The seed nuclei of this reaction, the stable 35Cl, acts as a
neutron poison in the nucleosynthesis processes during later burning phases of
stars. This makes the reaction important for astrophysical calculations, aiming to
36
reproduce the abundances of elements. Due to the long half-life of Cl, the cross
section and the production rate of the above reaction are also important for nuclear
technology and nuclear waste management.
The two main goals of this work are: (i) the production of an independent 36Cl/35Cl
standard for accelerator mass spectrometry (AMS); and (ii) the determination of the
Maxwellian averaged cross section (MACS) of 35Cl(n,J)36Cl at 25 keV using AMS.
Approaching the first goal, NaCl pellets were irradiated at the TRIGA Mark II reactor
at the ATI in Vienna and at the Budapest research reactor. The neutron flux was
monitored via the reference cross section of 197Au(n,J)198Au (gold foils attached to
176
and gold powder homogenously mixed into the pellets) and determined by activity
measurements on the foils and the pellets. With this data we calculated a 36Cl/35Cl
ratio for the irradiated samples.
The AMS measurements on these samples were performed at VERA (Vienna
Environmental Research Accelerator), relative to a standard from ETH Zurich. The
comparison of the 36Cl/35Cl ratio calculated from the activity measurements and
measured ratios by AMS shows a systematic discrepancy of 5%.
To determine the neutron capture cross section of 35Cl, AMS measurements were
performed on two samples, which were irradiated with neutrons of a MaxwellBoltzmann energy distribution of 25 keV at the Forschungszentrum Karlsruhe.
A preliminary mean value for the cross section is deduced by combining the AMS
data and the neutron-fluence. The relevant cross section for nucleosynthesis in
stars (MACS) will be calculated by weighting the mean value for the cross section
with a Maxwell-Boltzmann energy distribution of 25 keV.
The irradiation techniques and the measuring procedure by AMS will be discussed
and our new results will be compared with previous measurements of neutron
capture on 35Cl.
POS-FAKT-11
Temperature Dependent Nuclear Matter Approach
J. Haidvogl2, T. Srdinko1, D. Neudecker2 and H. Leeb2
1
Inst. of Atomic and Subatomic Phys., TU Wien, Wiedner Hauptstr. 8,
1040 Wien, [email protected],
2
Inst. of Atomic and Subatomic Phys., TU Wien, Wiedner Hauptstr. 8,
1040 Wien
The nuclear matter approach provides an effective interaction in the presence of a
sea of nucleons. Especially it accounts for the Pauli principle which forbids
scattering processes into the occupied states of the nucleonic see.
It is well suited to describe the bulk properties of nuclei as well as optical potentials
beyond 40 MeV incident energy. Difficulties in the description of nucleon-nucleus
reactions beyond 70 MeV may indicate the importance of excited doorway states for
reaction processes and therefore the optical potentials.
In this contribution we consider the g-matrix approach for excited nuclear matter.
The g-matrix is evaluated via the Bethe-Goldstone equation with an exact Pauli
operator accounting for excitations with arbitrary occupation distributions. The
features of the g-matrix with regard to changes in excitation are discussed.
177
POS-FAKT-12
Study of Colour-Suppressed Bs Decays in Belle
M. Valentan, W. Mitaroff and C. Schwanda
Austrian Academy of Sciences – Institute of High Energy Physics
Nikolsdorfer Gasse 18, A 1050 Vienna, Austria
[email protected]
Mesons containing the heavy fifth quark b (called “bottom” or “beauty”) are of
particular interest for investigations of the Standard Theory and beyond. Decays of
these mesons are studied in the Belle detector at the “Beauty Factory” KEKB, an
asymmetric e–e+ collider at the KEK Laboratory in Tsukuba, Japan. Tuning the
collider to a center-of-mass energy of 10.86 GeV opens the resonant production of
the (b anti-b) vector-meson 5S, decaying into Bs(*) + anti-Bs(*) pairs of mesons
composed of a b and an s (“strange”) quark-antiquark.
Object of this study are the exclusive decays Bs J/
, Bs J/
KS, and Bs D0 KS which are colour-suppressed (in addition to being Cabibbo-suppressed).
We present the experimental environment (KEKB accelerator and Belle detector),
the data samples (more than 100 fb–1 have been collected in 2005 - 09), and
techniques based on Monte Carlo simulation for extracting the signal events from
the background.
FAKT-13
Operation of the CMS Tracker at the Large Hadron Collider
W. Adam, T. Bergauer, M. Dragicevic, M. Friedl, R. Frühwirth, St. Hänsel,
M. Hoch, J. Hrubec, M. Krammer, M. Pernicka, E. Widl
[email protected]
The inner tracking detector of the Compact Myon Solenoid (CMS) Experiment at
CERN is the largest semiconductor tracking device built so far. It consists of more
than 25,000 individual silicon sensors with a total active area of almost 200 square
meters. Its design, construction and commissioning was a huge effort of more than
50 institutes around the world and lasted almost seven years. The institute of High
Energy Physics (HEPHY) of the Austrian Academy of Sciences contributed
significantly to this project since its beginning by working on both the silicon strip
and the pixel detectors.
With the start of normal operation of the Large Hadron Collider (LHC), the CMS
Tracker became operational as a scientific device and as part of the CMS
178
experiment during data taking. Operation experience is gained continuously as the
LHC delivers proton-proton collisions. In this presentation all critical systems of the
tracker will be summarized and performance data will be presented. These
numbers will show that both, the tracker and the whole experiment are working
extremely well. First physics plots are already emerging, like measurements of the
masses of different well-known particles. These measurements are helpful in
calibrating the detector to be well prepared for the discovery of new physics as the
LHC continues to deliver collision data.
FAKT-14
Kick response measurements during LHC injection tests and
early LHC beam commissioning
K. Fuchsberger1, M. Alabau Pons2, S. Fartoukh2, B. Goddard2, V. Kain2, M.
Meddahi2, F. Schmidt2 and J. Wenninger2.
1
CERN, Geneva, Switzerland, [email protected]
2
CERN, Geneva, Switzerland
The transfer lines from the SPS to the LHC, TI 2 and TI 8, with a total length of
almost 6 km are the longest ones in the world. For that reason even small
systematic optics errors are not negligible because they add up and result in an
injection mismatch in the LHC. Next to other lattice measurement methods Kickresponse measurements were the most important sources of information during the
early phases of beam commissioning of these transfer lines and the LHC ring. This
measurement technique was used to verify orbit-corrector and BPM gains as well
as to sort out optics errors. Furthermore fits to off-momentum kick response turned
out to be an appropriate method to establish a model for systematic errors of the
transfer line magnets. This poster shortly describes the tools and methods
developed for the analysis of the taken data and presents the most important
results of the analysis.
179
9.3 FKP – Festkörperphysik
POS-FKP-1
Investigation Of Precipitation Growth in Aluminium-Silver Alloys
via in-situ SAXS
J. Akbarzadeh * and H. Peterlik *
* University of Vienna, Faculty of physics,
Dynamics of Condensed Systems, Austria
Alloys have a big area of applications in engineering where they are mostly
exposed to extreme conditions. Therefore, the knowledge about the influence of
different parameters (e.g. high temperature exposition, external forces...) on their
structure and later on their mechanical properties is of great importance for their
production. In-situ small-angle x-ray scattering (SAXS) measurements offer the
possibility to study the structural behaviour of materials under various conditions.
In this work the temperature dependence of the precipitation growth was
investigated in-situ via SAXS by two alloys: Al2at.%Ag and Al6at.%Ag. Changes in
radii and the mean distance between the precipitations were, firstly, determined by
"Guinier-fits" and afterwards by using the "Hard-Sphere-Model" [1]. The results of
both calculation methods are depicted in graphics and are compared with each
other.
To realize the experiments, an x-ray transparent furnace was developed which
could be mounted on a tensile machine. Due to this furnace, the investigation of the
precipitations' shape modification in dependence of external load [2] and
temperature was possible. It was found that there were no measurable changes in
shape within a resolution limit of 1%.
References
[1]
J. S. Pedersen, Adv. Colloid Interface Sci. 70, 1997, 171-210
[2]
Gupta et al., Acta Mater. 49 (2001) 53-63
POS-FKP-2
Microstructural and Electrical Analyses of Oxygen
Diffusion into Iridium Metal Gates
A. Alexewicz1, C. Ostermaier1, G. Pozzovivo1, W. Schrenk1, M. Schmid2, L. Tóth3,
B. Pecz3, J.-F. Carlin4, M. Gonschorek4, N. Grandjean4, J. Kuzmik1, 5, D. Pogany1,
and G. Strasser1
1
Institute of Solid State Electronics, Vienna University of Technology
180
2
Institute of Applied Physics, Vienna University of Technology
3
Research Institute for Technical Physics and Material Science, Budapest
4
Institute of Quantum Electronics and Photonics, EPFL Lausanne
5
Institute of Electrical Engineering, SAS Bratislava
Iridium is used as gate metal for GaN-based In0,17Al0,83N/AlN barrier High Electron
Mobility Transistors (HEMTs) [1]. Before annealing, a high oxygen concentration
confined at the Ir/InAlN interface is detected, but neither an aluminium nor an
indium oxide interfacial layer has been formed. In this work we investigate the
annealing-induced diffusion of the oxygen-rich interlayer and its electrical effects on
the device. No stable iridium oxide forms – instead oxygen is able to diffuse out of
the interlayer into the iridium gate metal, thus the interlayer is reduced. Above
700°C a homogeneous oxygen concentration is observed in the iridium layer,
whereas at 500°C oxygen is distributed inhomogeneously. This behaviour is also
verified electrically.
The diffusion length of oxygen in evaporated iridium is only in the order of 1 nm for
2 minutes annealing at 500°C [2]. Therefore, oxygen cannot diffuse efficiently in
dense iridium at that temperature, so that oxygen diffusion, enhanced by crystal
defects and grain boundaries, is assumed. Annealing at 700°C increases the
diffusion length to about 100 nm [2] and allows homogenous diffusion of oxygen
into iridium, leading to the most complete removal of the oxygen interlayer, as seen
from the C-V-measurements. Additionally, the analysis of the microstructure proves
that the thickness of the InAlN/AlN barrier does not change after annealing and
metal does not diffuse into the barrier. That confirms the already proven robustness
of InAlN.
The rapid thermal annealing was performed for 2 minutes at 400°C, 500°C and
700°C. Two samples with different gate metals (iridium and nickel) are analysed in
order to investigate the dependence on the metal. High-Resolution Transmission
Electron Microscopy (HRTEM) gives detailed analysis of the microstructure at the
different interfaces. Electron Energy Loss Spectroscopy (EELS) shows the twodimensional element distribution in the samples. I-V- and C-V-measurements are
used to determine the electrical properties.
References
[1]
C. Ostermaier, G. Pozzovivo, W. Schrenk, M. Schmid, L. Tóth, B. Pecz,
J.-F. Carlin, M. Gonschorek, N. Grandjean, J. Kuzmik, D. Pogany, and G.
Strasser “Metal-related Gate Sinking due to Interfacial Oxygen Layer in
Ir/InAlN High Electron Mobility Transistors”, Applied Physics Letters 96,
263515 (2010)
[2]
C. U. Pinnow, I. Kasko, N. Nagel, S. Poppa, T. Mikolajick, C. Dehm, W.
Hösler, F. Bleyl, F. Jahnel, M. Seibt, U. Geyer, and K. Samwer “Influence
of deposition conditions on Ir/IrO2 oxygen barrier effectiveness“, Journal of
Applied Physics 91 (12), 9591 (2002).
181
POS-FKP-3
Dynamics of Strongly Correlated Fermi Fluids
H. M. Böhm, R. Holler, E. Krotscheck, and M. Panholzer
Institut fütTheoretische Physik, Johannes Kepler Universität Linz, Austria
To date, understanding the quantum properties of fermionic many-particle systems
forms a major challenge for both experimentalists as well as theorists. In the long
wave-lengths regime, Landau’s concept of elementary excitations provides an
elegant and powerful tool for describing the dynamic properties. It yields the wellknown two types of modes: a collective one (“zero-sound” in 3 He, and “plasmon” in
charged systems), plus a continuum of incoherent particle-hole excitations. At
higher wave-vectors, the collective mode enters this band and is strongly damped.
There seemed to be little room for further surprises in this field.
However, recent experiments [1] performed on a monolayer of liquid 3He report
the first observation of a roton-like minimum in a Fermi liquid. The collective mode
reappears as a well defined excitation beyond the particle-hole band. We explain
this re-emergence of the phonon (and predict a similar effect for the plasmon in
charged systems) at the large wave vector edge (i.e. the low energy edge) of the
particle-hole continuum from a manifestly microscopic theory.
Our formalism is based on variationally optimizing the time-dependent
fluctuations of the wave funcion. We derive energy dependent effective interactions
accounting for two-pair excitiations and show how the form of the density-density
response function must be changed from the paradigm of the RPA (random phase
approximation) form. State-of-the-art results for the static ground state structure are
used as an input.
This work was supported by the FWF under project nr. P21264-N20.
References
[1]
H. Godfrin, M. Meschke, H.J. Lauter, M. Meschke, H.M. Böhm,
E. Krotscheck, and M. Panholzer, J. Low Temp. Phys. 158, 147 (2010)
POS-FKP-4
3D Analysis of Nanocrystalline FeAl
C. Gammer1, C. Mangler1, H.-P. Karnthaler and C. Rentenberger3
1
Physics of Nanostructured Materials, Faculty of Physics,
University of Vienna, Boltzmanngasse 5, 1090 Wien, Austria
[email protected]
182
Nanocrystalline materials and nanostructures receive an increasing interest in
materials science, since they often show unexpected physical properties. Their
properties are closely linked to the size and 3D morphology of the nanostructures.
Conventional transmission electron microscopy (TEM) analysis tools provide
information on a projection of the nanostructures. Advanced analysis methods
based on TEM can be used to determine the 3D morphology. In the present work a
method based on TEM diffraction is developed that can be used to determine the
size and morphology of the coherently scattering domains in 3D.
In order to make bulk nanocrystalline materials several approaches have been
used; one of them is based on their production by severe plastic deformation.
Nanocrystalline intermetallic FeAl was made by high pressure torsion deformation
of B2 ordered Fe-45at.%Al. The obtained bulk samples allow cutting out samples
for TEM that can be directly linked to the shear direction and shear plane. Both,
planar and cross sections of nanocrystalline FeAl were investigated to study the
shape and morphology of the nanocrystals. In addition to the TEM images, electron
diffraction patterns were recorded with a large range of different tilting angles. The
morphology of the nanograins was analysed from the electron diffraction patterns
by applying different tilting angles of the incident beam. A modified Williamson Hall
plot was used to determine the coherently scattering domain size for each tilt angle.
The analysis of the diffraction patterns was carried out with the software PASADtools (www.univie.ac.at/pasad).
From the results it was possible to determine quantitatively the size and
morphology of the nanograins in 3D. The results show that the nanograins have a
ellipsoidal shape and are elongated in shear direction, which is in good agreement
with TEM images. In addition to the possibility to analyse nanostructures in 3D,
TEM provides conveniently the possibility to analyse locally selected areas of the
sample in contrast to X-ray diffraction methods. Furthermore, due to the strong
scattering factor, electron diffraction patterns can be recorded in seconds thus
allowing to cover a large range of tilting angles in a short time.
POS-FKP-5
Numerical Study of Photonic Crystal Slab Based
Quantum Well Infrared Photodetectors
R. Gansch1, S. Kalchmair1 and G. Strasser1
1
Institute for Solid State Electronics, TU Vienna, 1040 Vienna, Austria
Photonic Crystals (PhC) provide properties like photonic bandgaps or negative
refractive indices. By embedding a Quantum Well Infrared Photodetector (QWIP)
into a PhC slab these photonic bandgaps can be used to manufacture spectral
sensitive photonic detection devices in the mid infrared region.
The PhC slabs can be analyzed numerically by several methods such as the 2D
plain wave expansion method (PWEM) or 3D finite differences time domain (FDTD)
simulation. However these methods are either inaccurate or very time consuming.
183
The revised plain wave expansion method (RPWEM) combined with effective
refractive indices to account for mode guiding in the slab offers results with
great accuracy in a timely manner. Several devices were simulated employing
this algorithm and results were compared to real manufactured devices.
References
[1]
Zabelin, V., “Numerical Investigations of Two-Dimensional Photonic Crystal
Optical Properties, Design and Analysis of Photonic Crystal Based
Structures”, École Polytechnique Fédérale de Lausanne (2009)
POS-FKP-6
Magnetite Nanoparticles within a Semiconducting Matrix
P. Granitzer1, K. Rumpf1, M. Venkatesan2, A.G. Roca3, L. Cabrera3,
M.P. Morales3, P. Poelt4 and M. Albu4
1
Institute of Physics, Karl Franzens University Graz, Universitaetsplatz 5, 8010
Graz, Austria, [email protected]
2
Institute of Physics, Trinity College Dublin, College Greeen, Dublin 2, Ireland
3
Instituto de Ciencia de Materiales de Madrid, CSIC, Sor Juana Inés de la Cruz 3,
Cantoblanco, 28049 Madrid, Spain
4
Institute for Electron Microscopy, University of Technology Graz, Steyrergasse 17,
8010 Graz, Austria
Iron oxide nanoparticles are prepared by high temperature decomposition of iron
organic precursor. The particles which are fabricated with an average size between
5 and 10 nm are coated with a surfactant in solution. Silicon is used as matrix for
these monodisperse Fe3O4 particles to achieve a magnetic nanocomposite. For this
purpose a silicon wafer is porosified by anodization in aqueous hydrofluoric acid
solution. The iron oxide nanoparticles are infiltrated into the pores of the porous
silicon resulting in a (dispersed nanoparticle/semiconductor)-composite with
magnetic properties which are determined by the morphology of the silicon matrix
as well as the distribution of the particles within the individual pores. The Fe3O4
nanoparticles are superparamagnetic but the magnetic composite offers
ferromagnetic properties below a certain blocking temperature due to dipolar
coupling between the particles which can be influenced by the coating of the
particles and the concentration of the particle solution. Furthermore the magnetic
behaviour, especially the anisotropy between two magnetization directions
(magnetic field parallel and perpendicular to the pores, respectively) can be
modified by varying the morphology of the silicon matrix. The porous
silicon/magnetite composite offers not only interesting magnetic properties with an
adjustable transition temperature between superparamagnetic and ferromagnetic
behaviour but it is also a promising candidate for biomedical applications due to the
low toxicity of both materials.
184
POS-FKP-7
Spin Ensembles on a Chip: Collective Effects in Cavity QED
K. Henschel 1*, J. Majer 2, J. Schmiedmayer2 and H. Ritsch1
1
Institute for Theoretical Physics, Universität Innsbruck, Technikerstrasse 25,
A 6020 Innsbruck, Austria
2
Atominstitut, TU Wien, Stadionallee 2, A 1020 Vienna, Austria
*
Recipient of a DOC-fFORTE-fellowship of the Austrian Academy of Sciences
We study the dynamics of an ensemble of spins (two-level systems) coupled to a
resonant microwave cavity mode. The ensemble can consist in a cloud of ultracold
atoms or Nitrogen-Vacancy (NV) centers in a diamond. Despite the minute single
spin coupling one obtains strong coupling between collective states and microwave
photons enabling coherent transfer of an excitation between the long lived
ensemble qubit state and the mode. Evidence of strong coupling can be obtained
from the cavity transmission spectrum even at finite thermal photon number. In the
case of NV centers additional line broadening due to remaining (not converted)
Nitrogen in the crystal and NV-NV interactions have to be taken into account.
POS-FKP-8
Structure and Luminescence Properties of Eu-doped Y2O3 NanoParticles Prepared by Microwave Plasma Synthesis
A. Kautsch1, U. Brossmann1, H. Krenn2, F. Hofer3 and R. Würschum1
1
Institut für Materialphysik, TU Graz, 8010 Graz, Austria
Institut für Experimentalphysik, Karl-Franzens Universität, 8010 Graz, Austria
3
Institut für Elektronenmikroskopie, TU Graz, 8010 Graz, Austria
2
Rare-earth doped nano-crystalline oxides, e.g. Eu-alloyed Y2O3, offer attractive
prospects as novel luminescent materials. A small particle size is known to alter the
optical properties and is expected to contribute to an increased luminescence yield.
In the present study, pure and 3-12 at.-% Eu-doped Y2O3 with a uniform, small
initial grain size as a model system was for the first time prepared using low
temperature microwave plasma synthesis. The specimens were structurally
characterized by x-ray diffraction and transmission electron microscopy. The
photoluminescence, both of dry powder samples and dispersions, was studied for
excitation wavelengths in the UV and visible range.
As synthesized, the samples are nano-amorphous and show only weak
luminescence. The formation and growth of mixed Eu/Y oxide nano-crystals upon
185
annealing and the concomitant increase of the luminescence yield is studied for
different annealing temperatures and additions of Europium.
POS-FKP-9
Transporteigenschaften von Metall-Halbleiter separierten
einwandigen Kohlenstoff-Nanoröhrchen
M. Sauer1, W. Lang1, S. Puchegger1, H. Peterlik1, M. Havlicek2, W. Jantsch2,
M. Rümmeli3, H. Schalko4, K. Yanagi5, H. Kataura5, und H. Kuzmany1
1
Universität Wien, Fakultät für Physik, A-1090 Wien, Strudlhofgasse 4,
[email protected]
2
Johannes Kepler Universität Linz, Institut für Halbleiter- und Festkörperphysik,
A-4040 Linz
3
Leibniz Institut für Festkörperphysik und Werkstoffforschung, D-01069 Dresden
4
Technische Universität Wien, Institut für Sensor und Aktuatorsysteme,
A-1040 Wien
5
Tokyo Metropolitan University, Department of Physics, Tokyo, Japan
Einwandige Kohlenstoff-Nanoröhrchen sind bekannt für ihre besonderen
mechanischen und elektronischen Eigenschaften. In den Letzten Jahren ist es
gelungen metallisch leitende und halbleitende Röhrchen nahezu vollständig zu
trennen. Dies ergab eine neue Ausgangssituation für Transportuntersuchungen und
eine damit verbundene Herausforderung zur Untersuchung der ElektronenSpinresonanz (ESR).
In diesem Beitrag wird über Messungen der dc- und Hochfrequenzleitfähigkeit an
Kohlenstoff-Nanoröhrchen als Funktion der Temperatur berichtet. Die Röhrchen
wurden mit Hilfe eines nicht-magnetischen Katalysators bestehend aus PtRhRe
durch Laserablation hergestellt um später optimale Voraussetzungen für
Messungen der ESR zu gewährleisten. Anschließend wurden die metallischen und
halbleitenden Strukturen mit Hilfe von Dichtegradient-Ultrazentrifugierung getrennt.
Diese Vorgangsweise war analog zu jüngsten Untersuchungen an separierten
Nanoröhrchen, die mit magnetischen Katalysatoren hergestellt waren [1]. Aus
Messungen der Röntgenabsorption und der Abbildung im RasterElektronenmikroskop kann die effektive Probendicke ermittelt werden, die als
Grundlage für die Bestimmung der elektrischen Leitfähigkeit dient. Da das
separierte Material keine kompakte Struktur aufweist, sind die Ermittlungen der
tatsächlichen Massendichten wichtig. Leitfähigkeitsmessungen erfolgten zwischen
Raumtemperatur und 15 K. Die dc Leitfähigkeit der metallischen Röhrchen war bei
RT mehr als 30-mal höher als die der halbleitenden Röhrchen. Bei tiefen
Temperaturen war der Unterschied mehr als ein Faktor 700. Dieses Ergebnis zeigt,
dass nicht, wie bisher angenommen, der Übergangswiderstand zwischen den
Röhrchen ausschlaggebend für die elektrische Leitung ist, sondern sehr wohl die
intrinsische Leitfähigkeit der Röhrchen. Aus den Werten der Leitfähigkeit ergibt sich
für das Material der metallischen Röhrchen eine Skintiefe von 51 m bei
186
Raumtemperatur und 28.5 m bei 15 K. Diese Werte sind wesentlich größer als die
Dicke von 5-10 m der verwendeten Proben was seinerseits wieder entscheidend
für die Analyse von ESR Spektren ist. Die Temperaturabhängigkeit Leitfähigkeit der
halbleitenden Röhrchen war durch einen variable range hoping Prozess bestimmt.
Unterstützt durch den Fonds zur Förderung der Wissenschaftlichen Forschung in
Österreich, Projekt P21333-N20 und P20550
Literatur
[1]
K. Yanagi et al.,“Transport Mechanisms in Metallic and Semiconducting
Single-Walled Carbon Nanotubes”, unveröffentlicht (2010).
POS-FKP-10
Pulse – Heating Technique Results of Platinum Alloys Compared with
Modeling Results
S. Mehmood1, C. Cagran1, H. Sormann 2 and G. Pottlacher1
1
Institute of Experimental Physics TU Graz, Petersgasse 16, A-8010 Graz, Austria,
[email protected]
2
Institute for Theoretical Physics-Computational Physics, Petersgasse 16 II, A-8010
Graz, Austria
Platinum, a very precious metal, along with its alloys have many applications
technically and also in ornaments such as in jewellery. Their thermophysical
properties like density, heat capacity, thermal conductivity and surface tension play
an important role in casting processes and are required as input data for casting
simulation. The goal of this work is to investigate these properties and to simulate
them through modeling. Platinum and three typical jewellery alloys namely Pt-5Co,
Pt-5Ru and Pt-4Cu were investigated by an ohmic pulse heating technique [1].
This technique delivers thermophysical properties of electrically conducting
materials deep into the liquid phase. Heating rates up to 108 K/s are achieved, and
the liquid phase is achieved after about 30 μs. Within this short time the geometry of
the sample will neither be destroyed through force of gravity, instabilities nor other
effects, so that short-term measurements become possible on "standing” liquid
columns. These measurements allow the calculation of specific heat capacity and
the temperature dependencies of electrical resistivity, enthalpy, and density of these
alloys in the solid and liquid phase. Thermal conductivity and thermal diffusivity as a
function of temperature are estimated from resistivity data using the WiedemannFranz-law at the end of the solid phase and at the beginning of the liquid phase.
Based on the temperature-dependent experimental data listed above, model
calculations have been performed to achieve a deeper insight into the
thermodynamical behavior of these materials both within the high-temperature solid
and liquid regime. For such calculations, it is of special importance to choose model
functions that are both physically relevant and numerically robust [2].
187
References
[1]
Kaschnitz, E., Pottlacher, G. and Jäger, H., ’’ A New Microsecond PulseHeating System to Investigate Thermophysical Properties of Solid and Liquid
Metals ’’, International Journal of Thermophysics 13, 699-710 (1992)
[2]
G. Grimvall, in „Scientific Modeling and Simulations“ , vol. 15, edited by S.
Yip and T. Diaz de la Rubia (Springer-Verlag Berlin, 2009), pp. 5; 21; 41.
POS-FKP-11
Resonant Polarization Conversion and Extraordinary Transmission in
Photonic Crystal Slabs Covered with Metal
R. Meisels1, O. Glushko1, S. Kalchmair2 and G. Strasser2
1
Institute of Physics, University of Leoben, Leoben, Austria
Center for Micro- and Nanostructures, TU Vienna, Vienna, Austria
2
In this work we show that optical transmission through subwavelength holes in a
thin opaque metal layer can be substantially increased due to coupling of light to the
eigenmodes of a 2D photonic crystal (PhC) located directly under the metal layer.
The model system consists of a top gold layer and an underlying high-index
dielectric substrate. A hexagonal lattice of cylindrical air holes is then "etched"
through the gold layer and to some depth through the substrate. The parameters of
the PhC are a=3 m, r=0.3a, h=4 m, where a is the lattice constant, r is the radius
of the pores, and h is the depth of the pores. The system is excited by a plane-wave
incident normal to the surface. We define y to be the propagation direction; the
incident wave is polarized in z-direction (Ez 0, Hx 0).
The results of our 3D finite-difference time-domain (FDTD) calculations for the nearfield transmittance and reflectance are shown in Fig.1: We observe at least three
pronounced dips in reflectance (and corresponding peaks in transmittance) which
will be referred to as reflection dips 1, 2 and 3 corresponding to the notations in
Fig. 1.
188
It is important to note, that for the
given parameters 67% of the
1.0
surface is covered by the
0.9
reflecting gold layer. However,
0.8
the reflectance at =6.84 m (dip
0.7
3) is only 1%. The transmittance
0.6
is 60% which means that the
0.5
transmission efficiency, defined
0.4
2
as transmitted power per unit
0.3
0.2
area of the free surface (not
1
0.1
covered by gold) is 180%.
3
0.0
One can expect that each dip in
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
reflection should correspond to
Wavelength, Pm
gold layer
an enhanced field below the gold
layer. If we examine the
distribution of the electric field
within the PhC region we find that
dips 1 and 3 correspond to a high
amplitude of the Ey component
(which is absent in the incident
Fig. 1. Top: reflectance (solid) and transmittance
wave!) and the minimum of the
(dashed) spectra of the structure with 2D PhC with
dip 2 corresponds to a directly
a= 3 m, r=0.9 m, and h=4 m. Bottom: the
transmitted wave (high amplitude
distribution of the absolute values of the field
of the original Ez-component).
amplitudes of Ez (middle) and Ey (left and right)
For
a
quantitative
components (relative to the incident wave) at the
characterization
of
the
wavelengths corresponding to three reflection
polarization
conversion
the
dips. White corresponds to relative electric field
intensities
of
the
field
amplitudes >4.
components integrated over the
volume of the PhC were
2
2
calculated. We have obtained |Ey| /|Ez| =13.4 for the dip 3 and |Ey|2/|Ez|2=13.8 for
the dip 1. Another peculiarity of dips 1 and 3 is that the field has its maximal density
just below the gold layer while for dip 2 the Ez-field is maximal in the middle of the
pores. The yz cross sections of the absolute values of the corresponding electric
field components are shown in the lower part of Fig. 1.
By comparing reflectance spectra and field distributions obtained by the FDTD
method with results of plane-wave method calculations we show that dips 1 and 3
appear due to the coupling of incident light to dipole eigenmodes of the PhC at the
-point of the TM (E-field is parallel to the pores) band structure. This is confirmed
by the dependence of the positions of the dips on the radii of the pores and on the
refractive index of the PhC. A physical model explaining the coupling to TM modes
will be presented.
Transmittance experiments are performed in GHz region by using a 6.6 mm thick
ceramic plate with holes which is covered by a thin metal foil. The experiments
confirm the existence of the transmission peak 3 showing, however, a lower value
of the peak maximum.
T, R
Reflectance
Transmittance
This work was supported by the Austrian Nanoinitiative RPC PLATON.
189
POS-FKP-12
Metallic Nanotubes in Porous Silicon
K. Rumpf1, P. Granitzer1, M. Venkatesan2, P. Poelt3 and M. Albu3
1
Institute of Physics, Karl Franzens University Graz, Universitaetsplatz 5,
8010 Graz, Austria, [email protected]
2
Institute of Physics, Trinity College Dublin, College Greeen, Dublin 2, Ireland
Institute for Electron Microscopy, University of Technology Graz, Steyrergasse 17,
8010 Graz, Austria
3
In the frame of this work Ni is electrochemically deposited within the pores of
porous silicon. Typically the metal is precipitated as spherical, ellipsoidal or needlelike structures, exhibiting a diameter according to the pore-diameter of the matrix
and an elongation between 60 nm up to a few micrometers, depending on the
chosen process parameters. Additionally to these deposits small Ni-particles of a
few nanometers in size (2 – 6 nm) covering the pore-walls can be deposited under
certain conditions.
Electrodeposition, which in general is influenced by charge transfer and mass
transport of the reactants, allows various conditions. In choosing the parameters in
such a way that accompanying effects as e.g. capacity effects are negligible,
precipitates with spherical, ellipsoidal or needle-like shape can be fabricated. These
Ni-structures are more or less randomly but evenly distributed within the pores.
Furthermore small Ni-particles of a few nanometers in size can be precipitated,
which cover the pore walls and form a metal tube. Investigating the Ni covering of
the pore-walls more accurately a narrow distribution of these particles can be seen,
which means that the particle-particle distance is below 10 nm and thus assures
magnetic interactions. The small Ni particles are superparamagnetic but the dense
distribution leads to dipolar interaction which is also shown in the magnetic behavior
(e.g. coercivity, magnetic anisotropy). Thus the fabrication of ferromagnetic metal
wires as well as of metal quasi-tubes within porous silicon can be achieved.
POS-FKP-13
Temperature and Size Dependent properties of NiO
Nanoparticles
F. Shahzad1, P. Knoll1, K. Ettinger2, K. Nadeem1, I. Letofsky-Papst3, H. Krenn1,
K. Pressl1, Á. Kukovecz4, G. Kozma4 and Z. Kónya4
1
Institute of Physics, University of Graz, Universitätsplatz 5, 8010 Graz, Austria,
2
Institute of Earth Sciences, University of Graz, Universitätsplatz 2, 8010 Graz,
Austria
190
3
Institute for Electron Microscopy, Technical University, Graz, Steyrerg. 17,
8010 Graz, Austria
4
Department of Applied and Environmental Chemistry, University of Szeged,
Hungary
Raman spectroscopy can also be used to study the properties of magnetic
materials. A rather strong Raman signal is observed for antiferromagnetic spin
ordering due to strong exchange mechanism in these materials. For example, NiO
is an antiferromagnetic material with Néel temperature of 523K. There exists a 2magnon peak, at about 1500cm-1, in the Raman spectra of this material. The
behaviour of this 2-magnon peak is well understood for bulk NiO material. We have
studied its behaviour in nanoparticles of this material. [1]
NiO nanoparicles of different sizes (5-85nm) are prepared by Ball-milling and SolGel methods. All the samples are well characterised by XRD, TEM, EDX and
Rietveld refinement techniques [2,3]. Raman spectra are measured for all the
samples with in temperature range of 25K to 300K to monitor antiferromagnetic spin
ordering. These measurements have shown strong dependence of 2-magnon peak
on temperature and particle size. No 2-magnon peak is observed for nanoparticles
with sizes below 40nm, for larger size particles of 40nm and 85nm this peak
strengthens with decrease of temperature and again vanishes at temperatures
below 45K. [4]
Magnetic measurements are performed for all NiO nanoparticle samples by SQUID
magnetometer. Hysterisis curves are measured at different temperatures to observe
ferromagnetic spin ordering. To see more accurate temperature dependence,
Magnetisation vs. Temperature measurements are performed at constant external
fields. These measurements have shown the evidence of paramagnetic and
ferromagnetic spin ordering in NiO nanoparticles, which strengthen with decrease of
particles size and increase of temperature.[5]
References
[1]
M. Pressl, M. Mayer, P. Knoll, S. Lo and U. Hohenster, J. of Raman Spec
27, 343-349 (1996)
[2]
Y. Wu, Y. He, T. Wu, T. Chen, W. Weng and H. Wan, Materials Letters 61,
3174-3178 (2007)
[3]
G. Kozma, Á. Kukovecz, Z. Kónya, J. of Molecular structure 834-836, 430434 (2007)
[4]
N. Mironova-Ulmane, A. Kuzmin, et al., J. of Physics: conference series 93,
012039 (2007)
[5]
S.D. Tiwari, K.P. Rajeev, Thin solid films 505, 113-117 (2005)
191
POS-FKP-14
The Effect of Gating in Samples of Anti-Hall Bars within a Hall Bar
C. Uiberacker1, C. Stecher1 and J. Oswald1
1
Montanuniversität Leoben, Inst. f. Physik;
[email protected]
Due to the lack of realistic simulation tools for complicated quantum Hall samples
there are lots of experiments that are not fully understood yet. Already some years
ago R. G. Mani published an experiment using partial gating of a sample consisting
of an anti-Hall bar within a Hall bar, where he recorded a shift of the Hall resistance
transitions to lower magnetic fields, depending on the gating voltage. We use the
Nonequilibrium Network Model (NNM) [2-4] to simulate this ”anti-Hall bar within a
Hall bar” geometry and find the same qualitative behavior. Furthermore, by varying
the carrier concentration, the bare gating voltage and the curvature of saddles,
where tunneling leads to backscattering, and trying to fit the experimental curves,
we can reproduce the true values of these quantities which are hard to measure
directly.
References
[1]
R. G. Mani, “Dual Hall effects in inhomogeneous doubly connected
GaAs/AlGaAs heterostructure devices”, Appl. Phys. Lett. 70, 2879 (1997)
[2]
J. Oswald, “A new model for the transport regime of the integer quantum Hall
effect: The role of bulk transport in the edge channel picture”, Physica E 3,
30 (1998).
[3]
J. Oswald and M. Oswald, “Circuit type simulations of magneto-transport in
the quantum Hall effect regime“, J. Phys.: Condens. Matter 18, R101 (2006).
[4]
C. Uiberacker, C. Stecher, and J. Oswald, “Systematic study of nonideal
contacts in integer quantum Hall systems”, Phys. Rev. B 80, 235331 (2009).
POS-FKP-15
Optical Conductivity of Graphene in the THz Frequency Range
A. Urich1, T. Mueller1, J. Darmo1 and K. Unterrainer1
Vienna University of Technology, Institute of Photonics, 1040 Vienna, Austria
1
Since its discovery [1] in 2004, graphene - planar, hexagonal arrangements of
carbon atoms - attracted much attention in different scientific fields. This is not only
due to the fact, that truly two-dimensional crystalline systems like graphene were
supposed not to exist, but mainly due to the unique electronic properties of this
material.
192
The crystal structure of graphene consists of two equivalent sublattices. Quantummechanical hopping of electrons between these sublattices leads to the formation of
two energy bands that intersect at the points K and K'. Around these crossing
points, the electron dispersion relation is linear and gapless in contrast to
conventional metals and semiconductors. This fact is expected to result in strong
interaction between graphene and terahertz radiation under certain conditions, and
thus makes graphene a very interesting material for the terahertz spectral range. In
this context, the optical conductivity is a key property of graphene.
While the optical conductivity of graphene is constant for the visible spectral region,
it is expected to show strong deviation from this behaviour in the THz frequency
region [2]. This is due to the fact that interband transitions dominate in the visible
range whereas, below the mid-infrared range, intraband transitions are dominant.
We present an experimental approach to measure the optical conductivity of a
graphene monolayer by means of THz time-domain-spectroscopy involving an
on-chip coplanar waveguide structure for generation and detection of THz pulses.
References
[1]
Novoselov, K. et al., „Electric Field Effect in Atomically Thin Carbon Films“,
Science 306, 666 (2004)
[1]
Falkovsky, L. et al., „Optical far-infrared properties of a graphene monolayer
and multilayer“, Physical Review B 76, 153410 (2007)
193
POS-FKP-16
Optimization of Coupling into Slow Light Modes of Planar Silicon
Photonic Crystal Defect Waveguides in Aqueous Solutions
M. Wellenzohn1 and R. Hainberger1
1
AIT Austrian Institute of Technology GmbH, Health and Environment Department,
Nano Systems, Donau-City-Straße 1, 1220 Wien, E-mail:
[email protected]
In planar 2D photonic crystal defect (PhC) waveguides the backscattering
mechanism of light at each unit cell and omnidirectional reflection lead to the
formation of slow light modes [1],[2]. We want to exploit these slow light modes for
the development of a compact biophotonic sensor which is based on an integrated
optical waveguide Mach Zehnder interferometer (MZI). This biosensor will be used
for the detection of biomolecules such as proteins or DNA in aqueous solutions.
The PhC sensor arm of the MZI is covered with a thin biosensitive layer to which
only specific molecules can bind. This changes the phase velocity of the light, which
can be sensitively measured by the MZI. The theoretic detection limits of such
devices are as low as 0.1 pg/mm2 [3]. The slow light mechanism leads to a
significant enhancement of the interaction between light and the sensitive layer by
up to a factor of >100, which will allow reducing the sensing length of typically 1 cm
in conventional waveguide devices to ~100μm.
Achieving efficient coupling between a conventional wire waveguide mode and a
slow light mode in a PhC defect waveguide represents a challenging task in the
design of the sensor. A direct transition results in high losses. The major cause for
these losses is the impedance missmatch between the conventional and PhC
defect waveguide modes. For PhCs operated in air it has already been shown that
a short intersection a PhC defect waveguide of a few microns supporting a faster
mode can significantly enhance the coupling efficiency between the conventional
and PhC defect waveguide [4]. By modifying the lattice periods and the hole
diameters of this intersection PhC defect waveguide the group velocities can be
adapted such that the coupling losses are reduced significatly [5],[6].
Since the targeted compact biophotonic sensor operates in aqueous solutions we
optimized the coupling efficiency by means of extensive 2D Finite Difference Time
Method (FDTD) simulations employing the effective index approach. In order to
design a compact biophotonic sensor we used 3D Plane Wave Expansion Method
(PWE) simulations for calculating the PhC band structure and the defect modes.
While the majority of PhC devices are dedicated to telecom applications at 1550 nm
wavelength using an air cladding, we designed our PhCs for an operation
wavelength of 1310 nm, where the absorption in aqueous solutions is much lower
than at 1550 nm. For PhCs operated in water the coupling issue becomes even
more critical because the higher refractive index of water compared to air
considerably reduces the PhC working range.
194
We investigated PhC intersection areas with constant period lengths and
adipatically reduced periods. Our simulation results explicitly indicate the increase
of the coupling efficiency by the use of these concepts to reduce the impedance
mismatch between the conventional and PhC defect waveguide modes. As a result,
we obtained a new optimized PhC design for operation in aqueous solutions, which
has a high potential to become a key component of compact biophotonic sensors.
References
[1]
J.B. Khugin, and R.S. Tucker,” Slow Light” , Science and Applications CRC
Press (2009)
[2]
T.F. Krauss, “Slow light in photonic crystal waveguides“, Journal of Physics
D: Applied Physics 40 , 2666-2670 (2007)
[3]
R. Narayanaswamy, and O. S. Wolfbeis, “Optical Sensors“, Springer (2004)
[4]
J.P. Hugonin, P. Lalanne, T.P. White, and T.F. Krauss, “Coupling into slowmode photonic crystal waveguides”, Optics Letters, Vol. 32, No. 18, 26382640 (2007)
[5]
D. Bernier, E. Cassan, X. Le Roux, D. Marris-Morini, and L. Vivien,” Efficient
band-edge light injection in two-dimensional planar photonic crystals using a
gradual interface”, OE Letters Vol. 48(7), 070501-1 - 070501-3 (2009)
[6]
B. Momeni, and A. Adibi, ”Adiabatic matching stage for coupling of light to
extended Bloch modes of photonic crystals”, Applied Physics Letters 87,
171104-1 -171104-3 (2005)
POS-FKP-17
Analytical and Numerical Study on Surface Emitting Ring Lasers
T. Zederbauer1, E. Mujagi1, C. Schwarzer1, and G. Strasser1
1
Institute for Solid State Electronics, TU Vienna, 1040 Vienna, Austria
Grating coupled, surface emitting quantum cascade lasers (QCLs) featuring ring
cavities provide unique features such as low beam divergence, tuneability and a
circularly symmetric far field, which are highly desirable in many laser applications.
To successfully design well suited waveguides for different purposes a profound
knowledge of the waveguide resonant modes, the coupling constant, the
polarization, and the far field pattern is crucial.
In this work we present a numerical as well as an analytical approach to study and
optimize the waveguide's properties.
Far field patterns, polarization and mode distribution are acquired by performing 2D
and 3D numerical simulations using COMSOL Multiphysics [1,2].
Analytical results are obtained by the use of a Floquet-Bloch approach to calculate
mode distributions and coupling constants [3].
The numerical and analytical results are then compared and general rules for an
efficient waveguide and grating design are considered.
195
References
[1]
E. Mujagi, C. Deutsch, H. Detz, P. Klang, M. Nobile, A. M. Andrews, W.
Schrenk, K. Unterrainer, and G. Strasser, „Vertically emitting terahertz
quantum cascade ring lasers“, Appl. Phys. Lett. 95, 011120 (2009).
[2]
E. Mujagi, M. Nobile, H. Detz, W. Schrenk, J. Chen, C. Gmachl, and G.
Strasser, “Ring cavity induced threshold reduction in single-mode surface
emitting quantum cascade lasers”, Appl. Phys. Lett. 96, 031111 (2010).
[3]
N. Finger, W. Schrenk, E. Gornik, “Analysis of TM-polarized DFB laser
structures with metal surface gratings”, (2000) IEEE Journal of Quantum
Electronics, 36 (7), pp. 780-786.
9.4 GEP – Geschichte der Physik
POS-GEP-1
Leopold Gottlieb Biwald’s Physica Generalis
and the Tradition of its Sources
C. Faustmann
Recipient of a DOC-fellowship of the Austrian Academy of Sciences at the Institute
of Classical Philology, Medieval- and Neolatin Studies, University of Vienna
Dr. Karl Lueger-Ring 1, A-1010 Wien
[email protected]
Published in several editions since 1767/1768, widely used all across Europe and
officially designated for use at the universities and lyceums of the Habsburg
monarchy in accordance with an imperial decree [1] Leopold Gottlieb Biwald’s
Physica Generalis and Physica Particularis [2] held a place of particular significance
among the physics textbooks of the 18th century [3]. As Biwald’s compendium is
characterized by a special demand for being up-to-date, the author makes use of a
wide range of sources presenting the contemporary state of scientific research. In
particular Biwald goes back to 18th century textbooks which resemble his
compendium regarding the layout and the presentation of information – such as
works by Dalham, Hauser, Jaszlinszky, Lacaille, Mako, Mangold, Redlhamer, and
Scherffer. Furthermore, Biwald refers to more subject-specific publications of
current interest and in this context foremost to Boscovich’s publications. And as the
Physica Generalis and Particularis represent a textbook propagating Newtonian
physics above all, not only Newton’s Philosophiae Naturalis Principia Mathematica
but also several Newton-commentaries (especially publications by ’sGravesande,
Keill, Maclaurin, and Pemberton) are to be considered mentionable sources of
Biwald’s compendium.
196
In this presentation the connection between the Physica Generalis and its sources
is illustrated and particularly the relevance of the different types of sources for
Biwald’s textbook as well as the author’s own achievements regarding the reception
of relevant publications of 18th century physical technical literature are pointed out in
order to illustrate the importance of Biwald’s compendium at its time.
References
[1]
Kons. Akt. Fasz. I/2, Reg. Nr. 205 [presently: Archive of the University of
Vienna CA 1.2.206].
[2]
Biwald, L. G., “Physica Generalis”, Graecii 21769. – Biwald, L. G., “Physica
Particularis”, Graecii 21769.
[3]
Regarding positive estimations of Biwald’s compendium concerning this
matter cf.: Kunitsch, M., “Biographie des Herrn Leopold Gottlieb Biwald, der
Weltweisheit und Gottesgelehrtheit Doctor, ehemaliges Mitglied des
aufgelösten Jesuitenordens, ordentl. und öffentlicher Professor der Physik,
Senior und Director der philosophischen Facultät, und gewesener Rector
Magnificus an dem k. k. Lycäum zu Grätz”, Grätz 1808, 14f. – Valent, J.,
“Die Grazer Universität zur Zeit Josephs II. und die Lyzeumsjahre”, in:
Bausteine zu einer Geschichte der Philosophie an der Universität Graz
(Studien zur österreichischen Philosophie 33), ed. by Th. Binder et al.,
Amsterdam – New York 2001, 94. – Kernbauer, A., “Bildung und
Wissenschaft im Wandel”, in: Steiermark. Wandel einer Landschaft im
langen 18. Jahrhundert (Schriftenreihe der Österreichischen Gesellschaft
zur Erforschung des 18. Jahrhunderts 12), ed. by H. Heppner & N.
Reisinger, Wien – Köln – Weimar 2006, 381.
9.5 MBU – Medizinische Physik, Biophysik und Umweltphysik
POS-MBU-1
Brillouin Scattering in Ethanol-Water Mixtures
A. Asenbaum1, B. Kezic2, C. Pruner1,F. Sokolic2 and W. Emmerich1
1
Experimental Physics, University of Salzburg, Salzburg, AUSTRIA;
Department of Physics, University of Split, Split, CROATIA
2
We present Brillouin scattering measurements on ethanol-water mixtures at 293.15
K. The spectrometer was a 6-pass tandem Fabry-Perot interferometer with a
finesse of about 80, FSR = 15.00 GHz. The scattering angle was 90°. Ultrasonic
speed measurements at 3 MHz and index of refraction data at 514.5 nm are also
reported. Of particular note is the sound dispersion between 0.1 and 0.6 mole
197
fraction ethanol. The structural relaxation times derived from the experimental
Brillouin spectra in the region around 0.2 mole fraction are in rough agreement with
dielectric relaxation times.
POS-MBU-2
Brillouin Scattering in Lysozyme Solutions
A. Asenbaum1, C. Pruner1, E. Wilhelm1, A. Svanidze2,
S. Lushnikov2 and A. Schulte3
1
Experimental Physics, University of Salzburg, Salzburg, Austria;
A. F. Ioffe Physical Technical Institute, St. Petersburg, Russia;
3
University of Central Florida, Orlando, USA
2
We investigate the Brillouin spectrum of lysozyme solutions from 275 K to 335 K
and compare to the spectrum of water. A six-pass tandem Fabry-Perot
interferometer is used in both 90° and 180° geometries. Ultrasonic speed
measurements at 3 MHz are also reported. The lysozyme concentrations are 200
mg/ml and 250 mg/ml, respectively. For the lysozyme solution, the observed higher
values of the sound speed at GHz frequencies, as measured by Brillouin scattering,
could indicate additional relaxation processes as compared to pure bulk water,
where no sound dispersion between ultrasonic speed and hypersonic speed is
observed.
198
9.6 NESY – Physik an Neutronen und
Synchrotronstrahlungsquellen
POS-NESY-1
Dynamical Effects in the Determination of Diffusion Coefficients
from Scattering on isotopic Multilayers
F. Gröstlinger1, M. Leitner1, M. Rennhofer1 and B. Sepiol1
1
Dynamics of Condensed Systems, Universität Wien, Strudlhofgasse 4,
1090 Wien,
The L10 phase of FePt exhibits a large magnetocrystalline uniaxial anisotropy which
results in its high magnetic volume energy [1]. The magnetocrystalline and thermal
stability of this phase makes it a suitable candidate for ultrahigh density recording.
Thus detailed knowledge of the dynamic processes is essential for guaranteeing
sufficient long-term stability of the magnetic domains.
Nuclear Resonant Scattering (NRS) on isotopically varying but chemically
homogeneous multilayers allows us to study diffusion coefficients down to 10-25
m2s-1 with high resolution of the diffusion length [2]. Up to now only the kinematical
theory has been applied to evaluate the experimental data. However, this approach
was criticized in a recent paper [3], which led to further investigation considering
dynamical effects. We approached this by first calculating the change in the isotopic
density by solving the diffusion equation with von Neumann boundary conditions.
This density variation is discretized, fed into the standard software package
CONUSS [4], to calculate the reflectivity from FePt layered systems, and fitted to
our experimental data, as opposed to the kinematical theory which just compares
the integrated intensities of the superstructure peaks.
We conclude that for our samples these dynamical effects amount to a correction in
the diffusion coefficient of only 20%, resulting in a value of (1.4±0.3)·10-24 m2s-1 at
673K. In materials with a higher density of resonant scattering centres and less
absorption, though, the full dynamical theory for the determination of the diffusion
coefficients has to be applied.
References
[1]
J.B. Staunton et al., J. Phys.: Condens. Matter 16, 5623-5631 (2004)
[2]
M. Rennhofer et al., Phys. Rev. B 74 (10), 104301 (2006)
[3]
M.A. Andreeva, N.G. Monina, S. Stankov, Moscow Univ. Bull. 63 (2),
132-136 (2008)
[4]
W. Sturhahn, E. Gerdau, Phys. Rev. B 49, 9285-9294 (1994)
199
POS-NESY-2
Study of Novel Magnetic Materials Using the Usanspol Technique
E. Jericha1, G. Badurek1 and R. Grössinger2
1
Atominstitut, Vienna University of Technology, Stadionallee 2, 1020 Wien,
[email protected]
2
Institut für Festkörperphysik, Vienna University of Technology, Wiedner
Hauptstraße 8-10, 1040 Wien
USANPOL is a novel ultra-small-angle scattering technique with polarised neutrons
for investigation of magnetic materials. It represents a polarized neutron extension
to traditional USANS which works with unpolarised neutrons. The high angular
resolution of this technique relies and on the narrow reflection width of perfect
crystal reflections and is employed in a double-crystal diffractometer.
Corresponding to the μrad resolution of the set-up, micro-structures of the order of a
few tenths of a micrometre up to a few tens of micrometres may be investigated.
Neutron polarisation is achieved by insertion of birefringent magnetic prisms
between the monochromator crystal and the sample. Rocking the analyser crystal
produces a scattering pattern for both neutron spin states in a single measurement
but well separated in reciprocal space.
By this technique, we have recently studied various amorphous Galfenol softmagnetic ribbons which were produced by spinning from melt at different
manufacturing conditions. USANSPOL allows for a determination of domain sizes of
the non-magnetised samples and a study of the growing of magnetically
homogeneous regions with increasing externally applied magnetic field. The related
measurement series is a beautiful demonstration of range, capabilities and
structural size limits of the USANSPOL technique. The manufacturing process of
the ribbons is clearly reflected in the magnetic micro-structure of the different
specimens.
References
[1]
E. Jericha, G. Badurek, M. Trinker, “Ultra-small-angle scattering with
polarized neutrons”, Physica B 397, 88 (2007)
[2]
G. Badurek, E. Jericha, R. Grössinger, R. Sato-Turtelli, “Amorphous softmagnetic ribbons studied by ultra-small-angle polarized neutron scattering”,
Journal of Physics: Conf. Ser. 211, 012027 (2010)
200
POS-NESY-3
Holographically Prepared Diffraction Gratings
For Neutron Interferometry
1
2
1
3,4,
J. Klepp , C. Pruner , M. Fritzenwanker , H. Rauch
5
5
T. Nakamura ,
1
Y. Tomita and M. Fally
1Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria
2Department of Material Science and Physics, University of Salzburg, 5020
Salzburg, Austria, [email protected]
3Institut Laue Langevin, 6 rue Jules Horowitz, BP 165, F-38042 Grenoble Cedex 9,
France
4Atominstitut, Vienna University of Technology, Stadionallee 2, 1020 Vienna,
Austria
5University of Electrocommunications, Chofu-gaoka, Chofu, 1828585 Tokyo, Japan
We report on coherent elastic diffraction of thermal neutrons from gratings
holographically prepared in nano-particle-dispersed polymers [1]. In contrast to a
previously designed LLL-interferometer from polymethylmethacrylate (PMMA)
based gratings [2] or holographic polymer dispersed liquid crystals (HPDLC) [3]
these media offer a big variety of possibilities to optimize the diffraction properties
for beam splitters and mirrors [4]. Thus nanoparticle dispersed polymers prove to be
ideal materials for implementation as gratings in a neutron interferometer.
[1]
[2]
[3]
[4]
Y. Tomita, N. Suzuki, K. Chikama, Opt. Lett. 30, 839 (2005)
C. Pruner, M. Fally, R. A. Rupp, R. P. May, J. Vollbrandt, Nucl. Instr. Meth.
A 560, 598 (2006)
M. Fally, I. Drevensek-Olenik, M. A. Ellabban, K.P. Pranzas, J. Vollbrandt,
Phys. Rev. Lett. 97, 167803 (2006)
M. Fally, M. Bichler, M. A. Ellabban, I. Drevenšek Olenik, C. Pruner, H.
Eckerlebe and K. P. Pranzas, J. Opt. A 11, 024019 (2009)
POS-NESY-4
Nuclear and Incommensurate Magnetic Structure of NaFeGe2O6
Between 5K and 298K and New Data on Multiferroic NaFeSi2O6
G. J. Redhammer1, A. Senyshyn2,3, M. Meven2, G. Roth4, G. Tippelt1,
C. Pietzonka5, W. Treutmann6 and G. Amthauer1
201
1)
Abteilung für Mineralgie, Fachbreich Materialforschung & Physik, Universität Salzburg,
Hellbrunnerstr. 34, A-5020 Salzburg, Austria
2)
Forschungneutronenquelle Heinz Maier-Leibnitz (FRM II), Lichtenbergstrasse 1, D-85747
Garching, Germany.
3)
Fachgebiet Strukturforschung, Materialwissenschaft, Technische Universität Darmstadt,
Petersenstr. 23, D-64278 Darmstadt, Germany
4) I
Institut für Kristallographie, RWTH Aachen, Jägerstraße 17/19, D-52056 Aachen, Germany.
5)
Fachbereich für Chemie, Philipps-University Marburg, Hans Meerweinstr., D-35032 Marburg/
Lahn, Germany
6)
Institut für Mineralogie, Philipps-University Marburg, Hans Meerweinstr., D-35032 Marburg/ Lahn,
Germany
Pyroxene-type compounds are well known and studied in geo-science for decades.
They are important constituents of the upper mantle and have a rich crystal
chemistry, displaying several structural phase transitions as a function of
temperature, pressure and chemical composition. However, they also posses
interesting magnetic properties due to their low-dimensional structural
characteristics with infinite chains of transition metal bearing M1-octahedra; the
geometry of M1-octahedra and the interplay of magnetic moments within and
between these chains is determining the magnetic spin structure. Among the
members of the pyroxenes, one can find compounds with spin-gaps, pure ferro- and
pure antiferromagnets and even multiferroics. In the last few years, we have studied
in great detail the low temperature magnetic properties of the pyroxenes, among
2+
2+
2+
2+
3+
them CaM(Si,Ge)2O6 with M = Fe , Ni , Co and Mn , LiFe (Si,Ge)2O6
LiCrGe2O6, FeGeO3, MnGeO3 or CoGeO3 [1 and references therein). In the present
contribution we present results on the synthetic germanate-pyroxene NaFeGe2O6
and compare the results with the analogue silicate, also known as the fancy mineral
aegirine.
The compound NaFeGe2O6 was grown synthetically as polycrystalline powder and
as large single-crystals suitable for X-ray and neutron diffraction experiments to
clarify the low temperature evolution of secondary structural parameters and to
determine the low temperature magnetic spins structure. NaFeGe2O6 is isotypic to
the clinopyroxene-type compound aegirine and adopts the typical HT-C2/c
clinopyroxene structure down to 2.5 K. The Na-bearing M2 polyhedra were
identified to show the largest volume expansion between 2.5 K and room
temperature, while the GeO4 tetrahedra behave as stiff units and tend to shrink with
increasing temperature. Magnetic susceptibility measurements show a broad
maximum around 33 K, which marks the onset of low-dimensional magnetic
ordering. Below 12 K NaFeGe2O6 transforms to an incommensurately modulated
magnetic spin state, with k = [0.323, 1.0, 0.080] and a helical order of spins within
the M1-chains of FeO6 octahedra. This is determined by neutron diffraction
experiments on a single-crystal. Comparison of NaFeGe2O6 with NaFeSi2O6 is
given and it is shown that the magnetic ordering in the latter compound, aegirine,
also is complex and best is described by two different spin states, a commensurate
one with C2'/c' symmetry and an incommensurate one, best being described by a
spin density wave, oriented within the (1 0 1) plane.
202
References
[1]
Redhammer GJ, Roth G, Treutmann W, Hoelzel M, Paulus W, André G,
Pietzonka C, Amthauer G (2009a) The magnetic structure of clinopyroxenetype LiFeGe2O6 and revised data on multiferroic LiFeSi2O6. J Solid State
Chem. (doi: 10.1016/j.jssc.2009.06.013)
NESY-5
Optimisation of spatial neutron spin resonance
G. Badurek, Ch. Gösselsberger and E. Jericha
Atominstitut, Vienna University of Technology, Stadionallee 2, 1020 Vienna, Austria,
[email protected]
Drabkin's famous concept of spatial neutron spin resonance [1] is expanded to a
new type of neutron spin resonator. In combination with a pair of high performance
polarising devices a Drabkin-type resonator could be used not only as
monochromator with variable output wavelength at fixed take-off angle but also as
ultra-fast electronic chopper with arbitrary repetition rate and, even more important,
adaptive time-of flight resolution. In this case extremely flexible instruments for
neutron scattering experiments become feasible which will allow an almost
instantaneous variation of key machine parameters like the mean wavelength and
spectral width of the incident beam, and the overall time and energy resolution by
purely electronic means without any mechanical modification.
The original Drabkin-type spin resonator produces a spatially alternating magnetic
field by means of a meander-shaped conducting foil with fixed geometry. But the
neutron-chopping ability of our proposed new type of resonator requires an
assembly of individual, separately switchable modules [2]. However, using just a
sequence of separate current-sheets leads to a loss of field homogeneity due to
edge effects. Thus a well-balanced assembly, yielding sufficiently homogeneous
magnetic fields and satisfying simultaneously the requirements of fast electronic
switching, has to yet be developed. In order to find the optimal resonator
configuration we present a detailed analysis of various possible arrangements.
At first we intend to exploit the outstanding performance of such a type of neutron
spin resonator within the PERC project [3], which searches for new physics beyond
the Standard Model of particle physics at hitherto unrivalled level of sensitivity.
There the benefit of such a device will be an increased count rate because it allows
a replacement of the velocity selector and the chopper from the originally planned
“standard” set-up.
REFERENCES
[1] G.M. Drabkin, V.A. Trunov, V.V. Runov, “Static magnetic field analysis of a
polarised neutron spectrum”, Sov. Phys. JETP 27, 194-196 (1968)
203
[2] G. Badurek, E. Jericha, “Upon the versatility of spatial neutron magnetic spin
resonance”, Physica B 335, 215-218 (2003)
[3] http://www.physi.uni-heidelberg.de/Forschung/ANP/PERC/collaboration.php
9.7 OGD – Oberflächen, Grenzflächen und Dünne Schichten
POS-OGD-1
CuN Structures on Cu(110)
M. Hohage, M. Denk, and P. Zeppenfeld
Institut für Experimentalphysik, Johannes Kepler Universität Linz,
[email protected]
Chemisorption of atomic nitrogen on Cu(110) leads, at a saturation coverage of 2/3,
to the formation of a well ordered Cu(110)-(2x3)N reconstruction upon annealing at
650 K [1], [2].
An in-depth study concerning the formation of the nitrogen induced reconstruction
has been performed to address open questions regarding the exact structure of the
surface at the atomic scale.
In case the annealing temperature is below 550 K, a precursory Cu-N phase which
consists of elongated molecule-like structures, termed “CuN compounds”, has been
found on the surface by Scanning Tunneling Microscopy (STM). The CuN
compounds are characterised by their high mobility on the surface and have been
found to be stable up to at least 550 K. The compounds are expected to play a
crucial role in the formation of the final (2x3)N phase, as the Cu coverage of the
surface layer is increased to 4/3 as compared to the pristine Cu(110) surface.
A model structure for the CuN compounds has been derived from the analysis of
the STM images. The CuN compounds may consist of Cu4N subunits, which appear
as bright dots in the STM images.
References
[1]
D. Heskett, A. Baddorf and E. W. Plummer, Surf. Sci., 195, p. 94 (1988)
[2]
A. P. Baddorf and D. M. Zehner, Surf. Sci., 238, p. 255 (1990)
204
POS-OGD-2
AFM based Morphological and Electrical Characterization
of Hot Wall Epitaxy Grown 6P/SiO2
M. Kratzer1, S. Klima1, I. Beinik1, Q. Shen1, A. Lugstein2 and C. Teichert1
1
Institute of Physics, University of Leoben, Franz Josef Straße 18, A8700 Leoben,
Austria
2
Institut für Festkörperelektronik, TU Wien, Floragasse 7/1, A1040 Wien, Austria
In the present study, the growth of thin para-hexaphenyl (6P) films on silicon oxide
has been investigated. The 6P layers were fabricated by hot wall epitaxy (HWE) at
substrate temperatures ranging from 273K to 423 K. As substrates Si(100) wafers
covered with native or thermally grown oxide were used. The film morphology was
determined by conventional tapping mode atomic force microscopy (TM-AFM).
While the films grown at high temperature consisted of large domains formed by
upright standing molecules the low temperature grown films were essentially
amorphous and contained a number of additional structures. The influence of
temperature treatment on the morphology of the low temperature grown 6P films
was additionally investigated.
For electrical characterization, 6P layers were deposited onto SiO2 patterned with
Au electrodes. The so formed field effect transistor (FET) structures were
investigated by Conductive Atomic Force Microscopy (C-AFM) and Kelvin Probe
Force Microscopy (KPFM). The results were correlated with the film morphology.
Support by the Austrian Science Fund FWF is acknowledged.
Corresponding author: [email protected]
POS-OGD-3
Role of Surface Defects on Hydrogen Outgassing
of Stainless Steel
M. Leisch1, A. Juan2
1
Institute of Solid State Physics, Graz University of Technology, 8010 Graz, Austria,
2
Departamento de Fisica, Univ. National del Sur, 8000 Bahia Blanca, Argentina
Stainless steel (SS) is one of the most commonly used constructional materials for
vacuum chambers and components. Special applications like accelerator, storage
ring facilities or advanced semiconductor device processing make need for extreme
high vacuum (XHV). In the XHV regime a reduction of the outgassing rates of the
205
materials used in the construction of the vacuum system is essential. Beside
surface treatment to reduce the surface roughness high temperature vacuum firing
became an alternate method and widely accepted practice of reducing the amount
of hydrogen dissolved in SS. For the description of the outgassing rate basically two
models common as diffusion limited model (DLM) and recombination limited model
(RLM) have been discussed. Surface states which may influence the outgassing
kinetics significantly are not considered in the DLM. It is well established that the
rate of recombination depends strongly on the atomic structure of the surface and is
e.g. generally higher on stepped surfaces than on flat close packed planes. In order
to gain atomic level information on the real morphology of a surface after common
bake-out and vacuum firing SS samples were imaged in the atomic force
microscope (AFM) and the scanning tunnelling microscope (STM).
The main experimental work has been carried out on a combined STM – atom
probe field ion microscope (AP-FIM) apparatus [1]. A unique feature of the
particular combined instrument is that it allows a fully-predictive preparation of STM
probe tips in situ by FIM which is important for a reliable imaging of complex
surfaces.
The surface after vacuum firing shows significant reconstruction with formation of
large flat terraces which can be assigned to (111) planes. These terraces are
bounded by bunched steps and facets corresponding in orientation almost to (110)
planes and (100) planes. The deep grooved grain boundaries, facets and bunched
atomic steps represent very active sites for adsorption and recombination of
hydrogen. A close up view on the large (111) terraces by STM show that there are a
lot of vacancies too.
Theoretical studies and simulations on the interaction of hydrogen with lattice
imperfections provide a new insight in hydrogen outgassing. The energy
calculations [2] using the ASED method (Atom superposition and Electron
Delocalization) result in lower energy levels in tetrahedral sites in Fe vacancies. It
supports the picture that surface and subsurface defects form traps with different
energetic levels. They may control the recombinative desorption process and give
explanation for the observed hydrogen outgassing behaviour of stainless steel.
References
[1]
Stupnik A Frank P Leisch M Ultramicroscopy 109 (2009) 563
[2]
Rey Saravia D Juan A Brizuela G Simonetti S I J Hydrogen Energy 34
(2009) 8302
POS-OGD-4
Para-Sexiphenyl on Silicon Dioxide: Growth and Annealing
S. Lorbek1, Q. Shen1 and C. Teichert1
1
Institute of Physics, University of Leoben, A-8700 Leoben, Franz Josef Strasse 18,
[email protected]
206
Although progress has been made in the recent years in the understanding of
fundamental growth processes in organic molecular beam epitaxy, the underlying
details are still to be explored [1]. Especially, understanding of the island nucleation
on the substrate during the deposition of oligomere molecules is crucial for the
design of growth routes that will avoid an undesired formation of 3D structures. This
is important for the fabrication of electronic devices based on such organic
materials with well defined physical characteristics.
Here, sub-monolayers of the rod-like molecule para-sexiphenyl (p6P) have been
deposited onto the isotropic surface of SiO2 under ultra-high vacuum, resulting in
islands of almost upright standing molecules. Right after the deposition, a short
annealing step was performed with different time durations and at different
temperatures [2, 3]. As an effect due to this annealing the grown islands began to
shrink until their structure vanished completely. To investigate this process the
islands size, distribution, fractal dimension [4] and molecule orientation has been
studied by in-situ and ex-situ atomic force microscopy in intermittent and contact
mode [5].
References
[1]
G. Hlawacek, et al., “Characterization of Step-Edge Barriers in Organic ThinFilm Growth”, Science 321 (2008) 108
[2]
J. Yang, et al., “Ultrathin-Film Growth para-Sexiphenyl (I): Submonolayer
Thin-Film Growth as a Function of the Substrate Temperature”, Journal of
Physical Chemistry B 112 (2008) 7816
[3]
J. Yang, et al., “Ultrathin-Film Growth para-Sexiphenyl (II): Formation of
Large-Size Domain and Continuous Thin Film”, Journal of Physical
Chemistry B 112 (2008) 7821
[4]
F. Meyer zu Heringdorf, et al., “Growth dynamics of pentacene thin films”,
Nature 412 (2001) 517
[5]
S.N. Magonov, et al., “Phase imaging and stiffness in tapping-mode atomic
force microscopy”, Surface Science 375 (1997) L385
POS-OGD-5
Surface Morphology Investigations of Cellulose Films
O. Miškovi1,3, F. J. Schmied1,3, M. Djak2,3, R. Schennach2,3 and C. Teichert1,3
1
Institute of Physics, University of Leoben, Franz Josef Strasse 18, 8700 Leoben
2
Institute of Solid State Physics, Graz University of Technology, Petersgasse 16/2,
8010 Graz
3
CD-Laboratory for Surface Chemical and Physical Fundamentals of Paper
Strength, Graz University of Technology, Petersgasse 16/2, 8010 Graz
Pulp fibers are natural fibers that consist of cellulose fibrils, embedded in a
hemicellulose and lignin matrix. The nano- and microstructure of these fibers - as
207
well as its influence on the fiber-fiber bond strength - is not yet completely
understood. There are several bonding models proposed [1] but the major
mechanism is still unclear.
Like other biological samples, pulp fibers are not uniform and therefore show a wide
variety of different features like length, shape, diameter etc.. Therefore, the
properties of cellulose films as a function of film thickness have been analyzed.
Based on atomic force microscopy (AFM) investigations, a comprehensive
roughness analysis was performed, calculating root-mean-square roughness ,
lateral-correlation-length and the Hurst parameter .
First results are revealing changes in the surface morphology, depending on the
film thickness. Additionally, hemicellulose was spin-coated on the cellulose film and
its influence was investigated.
Supported by Lenzing AG and the Christian Doppler Research Society, Vienna,
Austria.
References
th
[1]
T. Lindström et al., 13 Fundamental Research Symposium, Cambridge,
(2005) 457
POS-OGD-6
A Comparative Study of Charge Transport and
Meyer-Neldel Rule In Fullerene Devices
M. Ullah1, A. Pivrikas2, C. Simbrunner1, G. J. Matt1, N. S. Sariciftci2 and H.Sitter1
1
2
Linz Institute of Organic solar cells, LIOS, JKU Linz, Austria.
We measure the charge carrier mobility using two techniques, in the bulk of
fullerene films using Charge Extraction by Linearly Increasing Voltage (CELIV)
technique [1] and at the interface of insulators using Organic Field Effect
Transistors (OFET) [2]. We observed that the electron mobility is at least two orders
of magnitude higher than hole transport in the C60 films prepared by thermal
evaporation. Electric field, carrier concentration and temperature dependences of
the electron mobility was measured using both methods. More than one order of
magnitude higher charge carrier mobility values are measured in OFET
configuration due to high charge carrier concentrations at the quasi 2D transport
near the dielectric interface. We comparatively present the carrier concentration and
electric field dependence of the charge carrier mobility in both devices. MeyerNeldel Rule (MNR) is observed in both fullerene devices [3,4]. Meyer-Neldel
energy, EMN = 35 meV, which is interpreted as disorder parameter [5], is the same
in both device geometries, which suggest that the level of disorder is similar in the
bulk of fullerene films and at the interface with insulators
208
References
[1]
A. Pivrikas, Mujeeb Ullah, Th. B. Singh, C. Simbruner, G. Matt, H. Sitter2and
N. S. Sariciftci , Organic Elecrtronics submitted.
[2]
Mujeeb Ullah, D. M. Taylor, R. Schwödiauer, H. Sitter, S. Bauer,
N. S. Sariciftci and Th. B. Singh, Journal of Applied Physics, 106, 114505
(2009).
[3]
Mujeeb Ullah, T.B. Singh, H. Sitter, N.S. Sariciftci, Applied Physics A,
Materials Science & Processing 97 (2009), 521.
[4]
Mujeeb Ullah, I. I. Fishchuk, A. Kadashchuk, P. Stadler, A. Pivrikas,
C. Simbrunner, V. N. Poroshin, N. S. Sariciftci, and H. Sitter, Appl. Phys.
Lett. 96,213306 (2010).
[5]
I. I. Fishchuk, A. K. Kadashchuk, J. Genoe, Mujeeb Ullah, H. Sitter,
Th. B. Singh, N. S. Sariciftci, and H. Bässler, Phys. Rev. B 81, 045202
(2010).
POS-OGD-7
High Mobility, Low Voltage Operating C60 Based n-type
Organic Field Effect Transistors
M. Ullah1, M. Irimia-Vladu2, M. Reisinger2, Y. Kanbur3, G. Schwabegger1,
R.Schwödiauer2, S. Bauer2, N. S. Sariciftci4 and H.Sitter1
2
Institute of Soft Matter Physics, SOMAP, JKU Linz, Austria.
3
Department of Polymer Science and Technology, Middle East Technical
University, Balgat, Ankara, 06531, Turkey
4
Linz Institute of Organic Solar Cells, LIOS, JKU Linz, Austria.
1
We have reported the state-of-the-art C60 based bottom gate-top contact transistors
by engineering different organic materials (BCB, Polyethylene and Adenine) / metaloxide (AlOx) bilayer as gate dielectric. The engineering of metal-oxide and organic
material passivation bilayer combines the advantages of having a high dielectric
metal oxide and a thin passivation layer of polymer or small molecule capped on
AlOx layer. The passivation layer helps both smoothing the dielectric surface and
suppressing the leakage current while providing good interface properties with the
semiconductor layers. This results in OFETs that operate at voltages less than 500
mV. The AlOx layers are readily processible from solution and cured at low
temperature, instead of traditionally sputtering or high temperature processing, thus
this process is suitable for low-cost organic field effect transistors (OFETs)
manufacture. The output characteristics of the OFETs show well saturation
behavior while the transfer characteristic display an on/off ratio in excess of 103.
The OFET devices have a high field effect mobility which ranges from 2 - 5 cm2/V s
for different passivation layers, with low threshold voltages ~ 0.02 V - 0.05 V.
209
References
[1]
Mujeeb Ullah, D. M. Taylor, R. Schwödiauer, H. Sitter, S. Bauer, N. S.
Sariciftci and Th. B. Singh, Journal of Applied Physics, 106, 114505 (2009).
[2]
P. Stadler, A. M. Track, M. Ullah, H. Sitter, G. J. Matt, G. Koller, T. B. Singh,
H. Neugebauer, N. S. Sariciftci, M. G. Ramsey, Organic Electronic 11
(2010), 207-211
POS-OGD-8
Organic Heterolayers: an in-situ GIXRD Study of Sexiphenyl and
Pentacene
M. Oehzelt1, G. Koller2, T.U. Schülli3, T. Haber4, R. Resel4, M.G. Ramsey2
and P. Zeppenfeld1
1
Institute of Experimental Physics, JKU Linz, Altenbergerstr. 69, 4040 Linz, Austria
[email protected]
2
Institute of Physics, KFU Graz, Universitätsplatz 5, 8010 Graz, Austria
3
CEA-Grenoble, SP2M/NRS, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France
4
Institute of Solid State Physics, TU-Graz, Petersgasse 12, 8010 Graz, Austria
Organic heterostructures of pentacene (5A) and para-sexiphenyl (6P) are studied
in-situ with X-ray diffraction methods. The single crystal copper (110) surface was
used as substrate to align the first molecular film uniaxially.[1] The deposited
pentacene molecules exhibit a high degree of order and serve as a template for the
second molecular layer. The sequence of layers was chosen in such a way that the
molecule with the lower sublimation temperature (5A) was overgrown by a
molecular layer with higher sublimation temperature (6P). XRD measurements of
the completed heterostructure reveal that the molecules orient within a few degrees
parallel to the direction of copper [1-10]. [2-3] The molecules in the second layer are
also crystalline and the long molecular axes of the 6P molecules follow closely the
directions of the underlying pentacene molecules. As the packing and orientation of
the crystalline layers is very similar it was possible to detect diffraction peaks of the
whole heterostructure on the same ccd-image simultaneously. Heating this
heterostructure to the sublimation temperature of pentacene, which is lower due to
its lower molecular weight compared to 6P, evaporates the pentacene molecules
through the 6P layer leaving only the 6P layer while keeping the original orientation
of the 6P molecules. A 2D-detector allows to study this evaporation process in-situ
and in real-time and can monitor the changes in both organic layers simultaneously.
The overgrown 5A layer is evaporated first due to its lower sublimation temperature.
During this process, the 6P rocking width increases, and fully recovers after the 5A
layer is gone. Moreover, the orientation of the 6P crystallites is not altered upon to
the evaporation process. It was thus possible to transfer a 6P(20-3) oriented layer
210
[5] onto Cu(110) whereas 6P deposited directly on the clean copper (110) substrate
crystallizes (62-9) oriented. [1]
References
[1]
M. Koini, et. al. in prep.
[2]
M. Oehzelt, G. Koller, J. Ivanco, S. Berkebile, T. Haber, R. Resel, F.P.
Netzer, M.G. Ramsey, Advanced Material 18, 2466 (2006)
[3]
G. Koller, S. Berkebile, J.R. Krenn, F.P. Netzer, M. Oehzelt, T. Haber, R.
Resel, M.G. Ramsey, Nano Letters 6, 1207 (2006).
[4]
M. Koini, T. Haber, O. Werzer, S. Berkebile, G. Koller, M. Oehzelt, M.G.
Ramsey, R. Resel, Thin Solid Films 517, 483 (2008).
[5]
M. Oehzelt, L. Grill, S. Berkebile, G. Koller, F.P. Netzer, M.G. Ramsey,
Chem. Phys. Chem. 8, 1707 (2007).
POS-OGD-9
Characterization of Individual ZnO Nanorods by
Atomic Force Microscopy
L. Wang1, I. Beinik1, M. Kratzer1, A. Djuriši2 and C. Teichert1
1
Institute of Physics, University of Leoben, Franz Josef Straße 18,
A 8700 Leoben, Austria
2
Department of Physics, University of Hong Kong, PR China
ZnO has come into focus of researchers due to its versatile physical and chemical
properties. Its wide band gap (3.37eV), large exciton binding energy (60meV at
room temperature), piezoelectricity and surface chemistry make ZnO an interesting
candidate for novel electronic devices.
In this study, the morphology and electrical properties of ZnO nanorods (NRs),
grown by hydrothermal synthesis and thermal evaporation on conductive substrates
were investigated by atomic force microscopy (AFM). Their resulting shape and
dimensions were determined by AFM in tapping mode. In order to get an insight in
the electrical properties, two-dimensional current maps at different bias voltages
were measured by conductive atomic force microscopy (C-AFM). Additional C-AFM
was utilized to determine the current-to-voltage (IV) characteristics of the top facets
of individual upright standing NRs. The C-AFM data was correlated with the
topography.
Support by the FWF project Nr. P19636 is acknowledged.
211
POS-OGD-10
Reaction of Methanol on ZnO modified Pd(111)
F. Weber1, M. Piffl1 and R. Schennach1
1
Institute of Solid State Physics, Graz University of Technology, Graz, Austria,
[email protected]
The reaction of methanol with water to form carbon dioxide and hydrogen is very
important for example for direct methanol fuel cells. As the electrodes of fuel cells
are very sensitive to CO poisoning a high selectivity for carbon dioxide is of the
utmost importance. In industry this reaction has been performed using a Cu/ZnO
catalyst [1]. While the selectivity and the activity of the catalyst is quite good, it
looses both over time due to sintering of the copper particles. Therefore people
changed to a Pd/ZnO catalyst. While Pd is known to be selective for carbon
monoxide formation, it was found that the Pd/ZnO catalyst shows even higher
selectivity towards carbon dioxide than the Cu/ZnO catalyst [2]. This surprising
result was attributed to the formation of a Pd/Zn alloy under reaction conditions,
possible due to partial reduction of the ZnO.
Here we will present results on the reaction of methanol on a Pd(111) surface
covered with ZnO islands as an invers model catalyst. The ZnO islands are
prepared by reactive Zn evaporation under an oxygen atmosphere. The structure of
the resulting ZnO islands has been investigated using scanning tunnelling
microscopy. The methanol reaction is studied using thermal desorption
spectroscopy and infra red reflection absorption spectroscopy.
The results of the methanol reaction will be presented and discussed with respect to
the available results in the literature.
References
[1]
Iwasa, N., Yamamoto, O., Akazawa, T., Ohyama, S., Takezawa, M.,
“Dehydrogenation of methanol to methyl formate over palladium/zinc oxide
catalysts”, J. Chem. Soc. Chem. Commun. 18 , 132 (1991)
[2]
Iwasa, N., Kudo, S., Takahashi, H., Masuda, S., Takezawa, N., “Highly
selective supported Pd catalysts for steam reforming of methanol”,Catal.
Lett. 19, 211 (1993)
212
POS-OGD-11
Time-Dependent Heat Conduction Problems Solved
by an Integral-Equation Approach
E. R. Oberaigner, M. Leindl and T. Antretter
Institute of Mechanics, University of Leoben, Franz-Josef-Strasse 18,
A 8700 Leoben, Austria
A classical task of mathematical physics is the formulation and solution of a timedependent thermoelastic problem. In this work we develop an algorithm for solving
the time-dependent heat conduction equation
c p Uw t T kT , ii
0
in an analytical, exact fashion for a two-component domain. By the Green's function
approach [1,2] the formal solution of the problem is obtained. As an intermediate
result an integral-equation for the temperature history at the domain interface is
formulated which can be solved analytically. This method is applied to a classical
engineering problem, i.e. to a special case of a Stefan-Problem [6]. The Green's
function approach in conjunction with the integral-equation method is very useful in
cases were strong discontinuities or jumps occur. The initial conditions and the
system parameters of the investigated problem give rise to two jumps in the
temperature field. Purely numerical solutions are obtained by using the FEM (finite
element method) [3] and the FDM (finite difference method) [5] and compared with
the analytical approach. At the domain boundary the analytical solution and the
FEM-solution are in good agreement, but the FDM results show a signicant
smearing effect.
References
[1]
Barton, G., “Elements of Green's Functions and Propagation”, Oxford
Science Pub.,Oxford, 1989
[2]
Butkovskiy, A.G., “Green’s Functions and Transfer Functions
Handbook”, Ellis Horwood Ltd., Chichester, 1982
[3]
Kikuchi, N., ”Finite Element Methods in Mechanics”, Cambridge University
Press, Cambridge, 1986
[4]
Lui, I-S., “Continuum Mechanics”, Springer-Verlag, Berlin, Heidelberg, New
York, 2002
[5]
Ozisik, M. N., “Finite Difference Methods in Heat Transfer”, CRC-Press,
Boca Raton, Florida, USA, 1994
[6]
Rubinstein, L.I., “The Stefan Problem”, Trans. Math. Mono. 27, Amer. Mat.
Soc., Providence, Rhode Island, USA, 1971
213
POS-OGD-12
Influence of Surface-Functionalized Nanoparticles on The Structural
Properties of Polymer Nanocomposites
S. Pabisch1, B. Feichtenschlager2, G. Kickelbick3 and H. Peterlik1
1
University of Vienna, Faculty of Physics, Boltzmanngasse 5, A 1090 Vienna,
Austria, E-mail: [email protected]
2
Vienna University of Technology, Institute of Materials Chemistry, Getreidemarkt 9,
A 1060 Vienna, Austria
3
Saarland University, Inorganic Solid State Chemistry, Dudweiler, Am Markt Zeile 3,
D 66125 Saarbrücken, Germany
Inorganic-organic polymer nanocomposites are a promising materials class for
many future applications e. g. the replacement of heavy weight materials by novel
light systems with similar or even better properties. [1] Furthermore, such novel
materials even comprise additional functionalities in fields like optics or electronics.
[2] The chemical parameters of the inorganic-organic building block surfacefunctionalization have an effect on the macroscopic properties of the materials and,
therefore, a detailed study of this influence gives novel insights into the importance
of surface-functionalization. Two types of nanoparticles, SiO2 and ZrO2, are
synthesized in two different particle sizes, one in the lower nanometer length scale
(5-15 nm in diameter) and one in the upper nanometer length scale (30-60 nm in
diameter). The compounds prepared and surface-functionalized are incorporated in
three different polymer matrices: epoxide resin, polyacrylate and polystyrene.
Structural characterization of the resulting nanocomposites is performed by small
angle X-ray scattering (SAXS): From the SAXS intensity, information on the size of
nanoparticles and their agglomeration behaviour is obtained. This work focuses on
the agglomeration behaviour of nanoparticles with different surface-functionalization
and different size embedded in three different polymer matrices.
References
[1]
H. Presting, U. König, Mater. Sci. Eng., C 2003, C23, 737
[2]
M. Tanihara, T. Miyazaki, S.-i. Ogata, C. Ohtsuki, in Handbook of OrganicInorganic Hybrid Materials and Nanocomposites, Vol. 2 (Ed.: H. S. Nalwa),
American Scientific Publishers, Stevenson Ranch, 2003, pp. 265
214
INDEX of PRESENTING AUTHORS
Abele, H.,
71, 72
Adaktylos, T.,
46, 65
Adam, G.,
61,159, 178
Ahmed, G.,
58, 83
Akbarzadeh, J.,
180
Akhtar, N.,
160, 161
Alam, K.,
123,128
Alexewicz, A.,
180
Alkofer, R.,
55, 64
Amenitsch, H.,
88, 93, 96
Andrews, A.M.,
91, 108, 109
Anjum, N.,
160, 161
Asenbaum, A.,
197, 198
Badurek, G.,
162, 200, 203
Bauer, G., P., S.
98, 107, 113, 141, 156, 209
Beinik, I.,
135, 153, 205, 211
Benedikt, M.,
56, 70, 88, 92
Bergauer, T.,
54, 61, 62, 84, 178
Berkebile, S.,
22, 28, 33, 137, 138
Bertel, E.,
134, 143
Besser, B.,
116, 117
Blank, M.,
55, 67, 68
Böhm, H.,
182
Bramwell, S.,
15, 19
Brehm, M.,
91, 113
Brossmann, U.,
185
Buchsbaum, A.,
89, 99
Chen, G.,
89, 101
Chen, X.
153
Chen, Z.-S.,
36
Cristofolini, P.,
42, 50
Cvetkovi, B.,
56, 69
Denk, M.,
134, 144, 204
215
Detz, H.,
91, 108, 109
Dragicevic, M.,
61, 62, 178
Dungel, W.,
21, 23, 27
Ellmeier, M.,
42, 48
Enzinger, E.,
35, 40
Erko, M.,
88, 94
Ernst, W.,
47, 49, 50, 155
Ertl, S.,
68
Fabjan, C.,
56, 71, 169
Faustmann, C.,
196
Federmann, S.,
168
Ferlaino, F.,
28, 31
Fleming, A.J.,
22, 133, 137, 138
Friedl, M.,
61, 62, 84, 168, 178
Friedreich, S.,
57, 78, 79
Frisch, W.,
58, 81
Fröschl, R.,
58, 82
Fuchsberger, K.,
54, 59, 179
Gall, J.,
134, 146
Gammer, C.,
182
Gansch, R.,
183
Geist, D.,
90, 103
Gfall, I.,
58, 84, 168
Giessen, H.,
14, 18
Gragnaniello, L.,
135, 152
Granitzer, P.,
184, 190
Greiner, M.,
7, 8
Grimm, R.,
14, 17, 27, 31
Gröstlinger, F.,
95, 199
Gruber, T.,
42, 49
Grumiller, D.,
68
Haas, G.,
28, 30, 121
Hartmann, O.,
57, 72
Haynl, I.,
135, 151
216
Henschel, K.,
163, 185
Hiesmayr, B.,
41, 44, 46, 52, 55, 65, 66
Hipp, F.,
46, 65
Hitzenberger, R.,
34
Hörmann, N.,
58, 81
Hofmann, W.,
125, 129, 132
Hohage, M.,
144, 146, 204
Huber, M.,
41, 44, 46, 52, 55, 65, 66
Huemer, E.,
54, 62
Hussain, M.,
123, 129
Irmler, C.,
84, 168
Jenke, T.,
57, 72
Jussel, P.,
55, 63
Južni
, S.,
116, 119
Kautsch, A.,
185
Kienberger, R.,
14, 16
Kiesenhofer, W.,
55, 64
Kirchsteiger, C.,
7, 8
Kiymaz, F.,
35, 38
Knünz, V.,
54, 62
Krammer, M.,
61, 62, 178
Krassnigg, A.,
55, 67, 68
Kratzer, M.,
153, 205, 211
Kremsner, A.,
51, 163
Krenn, H.,
89, 97, 100, 185, 190
Kreuzer, W.,
35, 36, 37
Kuhn, D.,
63, 170
Kumagai, O.,
14, 19
Kurfürst, C.,
169
Kuzmany, H.,
186
Lackner, F.,
42, 50
Lederer, C.,
57, 75
Lechner, R.,
89, 91, 98, 114
Leitner, M.,
88, 95, 199
217
Lettner, H.,
123, 125, 131
Libisch, F.,
29, 90, 104
Liko, D.,
81, 170
Lorbek, S.,
206
Lucha, H.,
171, 172
Madl, P.,
124, 132
Mair, K.,
57, 76, 175
Mandl, B.,
91, 110
Markum, H.,
116, 117
Marmiroli, B.,
88, 93, 96
Martschini, M.,
57, 77, 80, 173, 176
Massiczek, O.,
MayrhoferReinhartsgruber, M.,
Mehmood, S.,
57, 78, 79
187
Meisels, R.,
188
Mihocic, M.,
35, 39
Miškovi, O.
207
Mitaroff, W.,
178
Mittermayr, F.,
54, 59
Moldaschl, T.,
91, 111
Moser, A.,
90, 105, 147
Müller, T.,
25, 28, 32, 111
Müllner, P.,
58, 87, 175
Nadeem, K.,
89, 97, 100, 190
Neudecker, D.,
58, 82, 177
Oberaigner, E.R.,
213
Oehzelt, M.,
148, 210
Pabisch, S.,
214
Pagana-Hammer, B.,
28, 30, 121
Paris, O.,
21, 24, 94, 114
Parz, W.,
21, 25, 111
Pavetich, S.,
58, 77, 80, 173, 176
Penjweini, R.,
123, 126
Pfingstner, J.,
58, 85
135, 155
218
Pfleiderer, C.,
88, 92
Pichler, F.,
116, 119
Pichler, T.,
89, 102
Piffl, M.,
212
Pillmayr, N.,
7
Primetzhofer, D.,
29, 90, 107, 135, 141, 156
Pruner, C.,
197, 198, 201
Puschnig, P.,
21, 22, 147, 148
Radic, S.,
46, 65
Ramsey, M.,
22, 137, 138, 210
Ratschek, M.,
42, 47
Rauch, H.,
201
Redhammer, G.J.,
201
Reichl, C.,
134, 150
Reichsöllner, L.,
164
Resel, R.,
105, 134, 147, 148, 210
Rieckh, G.,
35, 36, 37
Ritsch, E.,
54, 63
Rumpf, K.,
184, 190
Rund, S.,
134, 141
Sauer, M.,
186
Saghafi, S.,
126
Sachslehner, F.,
22, 26
Schauberger, G.,
123, 124, 130
Schimpf, H.,
46, 65
Schmid, M.,
99, 134, 140
Schmid, P.,
121, 122
Schmidt, W.F.O.,
123, 124
Schöfbeck, R.,
15, 56, 60
Schreiner, S.,
116, 118
Schuster, P.-M.,
22, 26, 116, 120
Schwarz, C.,
7, 10
Schwarz, E.,
42, 51, 163
Shamim, K.,
166
219
Siddiqui, I.A.,
165
Simbrunner, C.,
134, 148, 208
Spengler, Ch.,
42, 46, 52, 65
Srdinko, T.,
82, 177
Strasser, G.,
25, 108, 109, 111, 180, 183, 188, 195
Suchorski, Y.,
134, 145
Sun, L.,
133, 138, 144, 146
Tanweer, I.S.,
166
Tautz, S.,
133, 136
Teichert, C.
147, 153, 154, 205, 206, 207, 211
Thim, H.,
116, 119
Thomas, M.,
7, 12
Thomay, C.,
54, 60
Uiberacker, C.,
41, 45, 90, 108, 192
Ullah, M.,
135, 157, 208, 209
Urich, A.,
192
Ursin, R.,
14, 17, 27
Valentan, M.,
84, 168, 178
Wagner, M.,
133, 137
Wagner, T.,
133, 139
Waldner, H.M.,
46, 65
Waltenberger, W.,
56, 70
Wang, L.,
211
Wang, X.,
57, 74
Waubke, H.,
35, 36, 37
Weber, F.,
212
Wegscheider, M.,
89, 101
Weidlinger, G.,
134, 138, 146
Weihs, G.,
41, 43, 50
Weinwurm, G.,
7, 10
Wellenzohn, M.,
194
Widhalm, L.,
121, 122
Widl, E.,
54, 60, 61, 178
Wilflinger, T.,
124, 131
220
Wünschek, B.,
57, 74
Zederbauer, T.,
195
221

60 Annual Meeting Austrian Physical Society 6–10 September 2010

Transcription

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