Philippe Wernet
Transcription
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?” 2 Understand the elementary steps of photochemical reactions 3 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… 4 Resonant Raman scattering Resonant state Optical/IR Vibrational X-ray Excited state Electronic Ground state 5 RIXS Valence levels hνin hνout Core level Energy transfer ΔE = hνin - hνout • Probing the frontier orbitals • Element- and site-specific • Locally at absorbing atom 6 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 7 1. Predict photochemical processes 8 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). 9 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). 10 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 11 MLn MLn-1 Ligand Time/distance R. Hoffmann, Angew. Chem. Int. Ed. Engl. 21, 711-724 (1982). 12 Fe(CO)5 Fe(CO)4 fragments Fe L3-absoprtion edge Delays between 0 and 700 fs mashed together for the moment! 13 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). 14 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) 15 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). 16 Excited Triplet Ligated • Coupling to vibrational manifold • Due to spin-orbit interaction • Fast energy dissipation • Veenendaal, PRL 104, 067401 (2010). 17 Predict photochemical processes Saillard, Hoffmann, JACS 106, 2006 (1984). 18 2. Explain photochemical catalysis 19 Canton et al. (Bressler, Sunstroem, Nielsen), Nature Communications 6, 6359 (2015). 20 3. Understand the local chemical interactions in metalloproteins 21 22 Kurashige, Chan, Yanai, Nat. Chemistry 5, 660 (2013). 23 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). 24 There are dozens of essential model compounds to be studied per metalloprotein… 25 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 26 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 27 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 28 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) 30 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 31
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