Finding intersections between electronic excited state potential energy surfaces with simultaneous ultrafast X-ray scattering and spectroscopy

Kasper S. Kjær*, Tim B. Van Driel, Tobias C.B. Harlang, Kristjan Kunnus, Elisa Biasin, Kathryn Ledbetter, Robert W. Hartsock, Marco E. Reinhard, Sergey Koroidov, Lin Li, Mads G. Laursen, Frederik B. Hansen, Peter Vester, Morten Christensen, Kristoffer Haldrup, Martin M. Nielsen, Asmus O. Dohn, Mátyás I. Pápai, Klaus B. Møller, Pavel ChaberaYizhu Liu, Hideyuki Tatsuno, Cornelia Timm, Martin Jarenmark, Jens Uhlig, Villy Sundstöm, Kenneth Wärnmark, Petter Persson, Zoltán Németh, Dorottya Sárosiné Szemes, Éva Bajnóczi, György Vankó, Roberto Alonso-Mori, James M. Glownia, Silke Nelson, Marcin Sikorski, Dimosthenis Sokaras, Sophie E. Canton, Henrik T. Lemke, Kelly J. Gaffney

*Corresponding author for this work

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Abstract

Light-driven molecular reactions are dictated by the excited state potential energy landscape, depending critically on the location of conical intersections and intersystem crossing points between potential surfaces where non-adiabatic effects govern transition probabilities between distinct electronic states. While ultrafast studies have provided significant insight into electronic excited state reaction dynamics, experimental approaches for identifying and characterizing intersections and seams between electronic states remain highly system dependent. Here we show that for 3d transition metal systems simultaneously recorded X-ray diffuse scattering and X-ray emission spectroscopy at sub-70 femtosecond time-resolution provide a solid experimental foundation for determining the mechanistic details of excited state reactions. In modeling the mechanistic information retrieved from such experiments, it becomes possible to identify the dominant trajectory followed during the excited state cascade and to determine the relevant loci of intersections between states. We illustrate our approach by explicitly mapping parts of the potential energy landscape dictating the light driven low-to-high spin-state transition (spin crossover) of [Fe(2,2′-bipyridine)3]2+, where the strongly coupled nuclear and electronic dynamics have been a source of interest and controversy. We anticipate that simultaneous X-ray diffuse scattering and X-ray emission spectroscopy will provide a valuable approach for mapping the reactive trajectories of light-triggered molecular systems involving 3d transition metals.

Original languageEnglish
JournalChemical Science
Volume10
Issue number22
Pages (from-to)5749-5760
Number of pages12
ISSN2041-6520
DOIs
Publication statusPublished - 2019

Cite this

Kjær, K. S., Van Driel, T. B., Harlang, T. C. B., Kunnus, K., Biasin, E., Ledbetter, K., ... Gaffney, K. J. (2019). Finding intersections between electronic excited state potential energy surfaces with simultaneous ultrafast X-ray scattering and spectroscopy. Chemical Science, 10(22), 5749-5760. https://doi.org/10.1039/c8sc04023k