Philippe Wernet

Mapping chemical interactions and dynamics with
soft x-ray laser spectroscopy
Philippe Wernet
Institute for Methods and Instrumentation for Synchrotron
Radiation Research
Helmholtz-Zentrum Berlin für Materialien und Energie
European XFEL and DESY Photon Science Users’Meeting, January 2016
…or…
“Why should we do RIXS with
soft x-rays at XFELs?”
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Understand the elementary steps
of photochemical reactions
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1. What are we probing with soft x-ray RIXS?
2. This defines three science cases I find
particularly worthy to be addressed!
3. Some words about the impact of such
studies…
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Resonant Raman scattering
Resonant state
Optical/IR
Vibrational
X-ray
Excited
state
Electronic
Ground state
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RIXS
Valence levels
hνin
hνout
Core level
Energy transfer
ΔE = hνin - hνout
• Probing the frontier orbitals
• Element- and site-specific
• Locally at absorbing atom
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We are probing:
• Where the valence electrons and holes are!
• How the valence electrons form bonds!
• How the valence orbitals are populated
• How the valence orbitals interact
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1. Predict photochemical processes
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3d TM complexes (metal carbonyls)
d8
d6
d7
Predictable ground-state structure
Elusive excited-state behavior
T. Langmuir, Science 54, 59-67 (1921).
R. Hoffmann, Angew. Chem. Int. Ed. Engl. 21, 711-724 (1982).
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Time-resolved RIXS at LCLS
„16-electron catalyst“
Out
Fe C O
<100 fs
In
1 mol/l in EtOH
K. Kunnus et al. Rev. Sci. Instrum. 83, 123109 (2012).
Ph. Wernet et al. Nature 520, 78-81 (2015).
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CO
2π*
Fe(CO)5
Fe(CO)4
2π*
dσ*
ΔE
5σ*
dπ
dσ*
dπ
5σ
ΔE is what we measure
• With soft x-ray RIXS
• Locally at the Fe atom
• At the Fe L absorption edge
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MLn
MLn-1
Ligand
Time/distance
R. Hoffmann, Angew. Chem. Int. Ed. Engl. 21, 711-724 (1982).
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Fe(CO)5
Fe(CO)4 fragments
Fe L3-absoprtion edge
Delays between 0 and 700 fs
mashed together for the moment!
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Fe(CO)5
Fe(CO)4 fragments
Early
Late
Ph. Wernet, K. Kunnus, I. Josefsson, I. Rajkovic, W. Quevedo, M. Beye, S. Schreck, S.
Grübel, M. Scholz, D. Nordlund, W. Zhang, R. W. Hartsock, W. F. Schlotter, J. J. Turner, B.
Kennedy, F. Hennies, F. M. F. de Groot, K. J. Gaffney, S. Techert, M. Odelius, A. Föhlisch,
Nature 520, 78-81 (2015).
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Fe(CO)4
Excited (E)
Excited +
Triplet (T)
Ligated (L)
Fit I(exp)i=1,…,4 with I(calc)i=1,…,4
I. Triplet (T): 300±100 fs
II. Excited (E): Within resolution
III. Ligated (L): 200±100 fs
 Reaction pathways
Ground state
(bleach)
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Experiment
Theory
Ab initio quantum chemistry calculations of 3d TM x-ray spectra
M. Odelius, Stockholm University
I. Josefsson et al., J. Phys. Chem. Lett. 3, 3565 (2012).
S. Bokarev, O. Kühn, Universität Rostock
E. Suljoti et al. Angew. Chem. Int. Ed. 52, 1 (2013).
M. Guo, M. Lundberg, Uppsala University
R. V. Pinjari et al., J. Chem Phys. 141, 124116 (2014).
D. Maganas, F. Neese, Max-Planck Institute for Chemical Energy Conversion
M. Roemelt et al., J. Chem. Phys. 138, 204101 (2013).
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Excited
Triplet
Ligated
• Coupling to vibrational
manifold
• Due to spin-orbit
interaction
• Fast energy dissipation
• Veenendaal, PRL 104,
067401 (2010).
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Predict photochemical processes
Saillard, Hoffmann, JACS 106, 2006 (1984).
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2. Explain photochemical catalysis
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Canton et al. (Bressler, Sunstroem, Nielsen), Nature Communications 6, 6359 (2015).
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3. Understand the local chemical
interactions in metalloproteins
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Kurashige, Chan, Yanai, Nat. Chemistry 5, 660 (2013).
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X-ray diffraction structure
Umena et al., Nature 2011
Refined structure
Beam damage confirmed by Suga et al., Nature 2015
Kurashige, Chan, Yanai, Nat. Chemistry 5, 660 (2013).
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There are dozens of essential
model compounds to be studied
per metalloprotein…
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Beam damage
• Redox damage by electrons, ions, and radicals
MnII
Mn2+ (d5)
MnIII
Mn3+ (d4)
MnIV
Mn4+ (d3)
• Electronic damage
– Valence excitations
– From scattered Auger and photoelectrons
– And from sequential multiphoton absorption
• Coulomb explosion
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Redox-active 3d TM complexes with XFEL soft RIXS
“The ideal RIXS experiment for redox-active samples”
1 mM, E/ΔE = 1000
• 100 kHz
• 50 fs pulses
• 0.1 µJ/pulse = 1014 photons/s
• 1 pulse/sample volume
• At typical jet flow rates (electrospinning jet)
• For a 5 x 5 µm2 spot
• 0.4 J/cm2 = 0.1 photons/molecule (5 % multiply excited Mn4)
• 1013 W/cm2
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Hydrogenase
Nitrogenase
Photosystem II
Cytochrome C
oxidase
Let‘s leave behind the ball-and-stick picture and have a look at the orbitals!
“New Science Opportunities Enabled by LCLS-II X-ray Lasers”, SLAC-R-1053
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Combine
• Innovative methods and instruments
• Theory
• Systematics
http://www.carl-zeiss-stiftung-125jahre.de
Orbital-specific mapping of chemical interactions and dynamics
Ph. Wernet et al., Nature 520, 78-81 (2015)
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Thank you
Kristjan Kunnus, Alexander
Föhlisch, HZB
Simone Techert
DESY
Michael Meyer
European XFEL
Kelly Gaffney, Uwe Bergmann,
Bill Schlotter, Josh Turner
SLAC, Stanford
Junko Yano, Jan Kern, Vittal
Yachandra
LBNL, Berkeley
Athina Zouni
HU Berlin
Marcus Lundberg
Uppsala University
Helmholtz Virtual Institute
Michael Odelius
Stockholm University
Frank De Groot
Utrecht University
Franz Hennies
MAX-Lab, Lund
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