Anisotropy enhanced X‐ray scattering from solvated transition metal complexes |
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Authors: | Elisa Biasin Tim B van Driel Gianluca Levi Mads G Laursen Asmus O Dohn Asbjørn Moltke Peter Vester Frederik B K Hansen Kasper S Kjaer Tobias Harlang Robert Hartsock Morten Christensen Kelly J Gaffney Niels E Henriksen Klaus B Møller Kristoffer Haldrup Martin M Nielsen |
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Institution: | 1. Department of Physics, Technical University of Denmark, Fysikvej 307, DK-2800Kongens Lyngby, Denmark;2. PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, CA94025, USA;3. Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA94025, USA;4. Department of Chemistry, Technical University of Denmark, Kemitorvet 207, DK-2800Kongens Lyngby, Denmark;5. Faculty of Physical Sciences, University of Iceland, Reykjavik, Iceland;6. Department of Chemical Physics, Lund University, Box 118, S-22100Lund, Sweden |
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Abstract: | Time‐resolved X‐ray scattering patterns from photoexcited molecules in solution are in many cases anisotropic at the ultrafast time scales accessible at X‐ray free‐electron lasers (XFELs). This anisotropy arises from the interaction of a linearly polarized UV–Vis pump laser pulse with the sample, which induces anisotropic structural changes that can be captured by femtosecond X‐ray pulses. In this work, a method for quantitative analysis of the anisotropic scattering signal arising from an ensemble of molecules is described, and it is demonstrated how its use can enhance the structural sensitivity of the time‐resolved X‐ray scattering experiment. This method is applied on time‐resolved X‐ray scattering patterns measured upon photoexcitation of a solvated di‐platinum complex at an XFEL, and the key parameters involved are explored. It is shown that a combined analysis of the anisotropic and isotropic difference scattering signals in this experiment allows a more precise determination of the main photoinduced structural change in the solute, i.e. the change in Pt—Pt bond length, and yields more information on the excitation channels than the analysis of the isotropic scattering only. Finally, it is discussed how the anisotropic transient response of the solvent can enable the determination of key experimental parameters such as the instrument response function. |
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Keywords: | time‐resolved anisotropic scattering orientational selection XFEL ultrafast molecular structure |
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