Shake-Down Spectroscopy as State- and Site-Specific Probe of Ultrafast Chemical Dynamics

Tracking the multifarious ultrafast electronic and structural changes occurring in a molecule during a photochemical transformation is a challenging endeavor that benefits from recent experimental and computational progress in time-resolved techniques. Measurements of valence electronic states, which provide a global picture of the bonding structure of the molecule, and core electronic states, which provide insight into the local environment, traditionally require different approaches and are often studied separately. Here, we demonstrate that X-ray pulses from a seeded free-electron laser (FEL) enable the measurement of high-resolution, time-resolved X-ray photoelectron spectra (XPS) that capture weak satellite states resulting from shake-down processes in a valence-excited molecule. This approach effectively combines the advantages of both valence- and core-state investigations. We applied this method to investigate photoexcited CS<sub>2</sub> molecules, where the role of internal conversion (IC) and intersystem crossing (ISC) in determining the predissociation dynamics is controversial. We present XPS spectra from photoexcited CS<sub>2</sub>, obtained at the FERMI FEL. High-resolution measurements, compared to the corresponding spectra obtained from accurate multireference quantum chemical calculations, reveal that shake-down satellite channels are highly sensitive to both valence electronic and geometric changes. Previous studies of the predissociation dynamics have led to uncertain assignments of the branching between singlet and triplet excited states. We derive a propensity rule that demonstrates the spin-selectivity of the shake-downs. This selectivity allows us to unequivocally assign contributions from the bright and dark singlet excited states, with populations tracked along the predissociation dynamic pathway.

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Journal
Journal of the American Chemical Society
Published
2025-09-02
DOI
https://doi.org/10.1021/jacs.5c09162
Citations
1
Primary Topic
Electron and X-Ray Spectroscopy Techniques
Type
article
Field-Weighted Citation Impact
0.66

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article

Shake-Down Spectroscopy as State- and Site-Specific Probe of Ultrafast Chemical Dynamics

Daniel Rolles, Oksana Plekan, Felix Allum, Cesare Grazioli et al.
1 citations
Journal of the American Chemical Society
Electron and X-Ray Spectroscopy Techniques
0.66
article

Shake-Down Spectroscopy as State- and Site-Specific Probe of Ultrafast Chemical Dynamics

Daniel Rolles, Oksana Plekan, Felix Allum, Cesare Grazioli, Michele Di Fraia, Marco Zangrando, Piero Decleva, Nitish Pal, Marcello Coreno, M. Danailov, Michele Devetta, Michael S. Schuurman, Richard J. Squibb, C. Vozzi, Ruaridh Forbes, Russell S. Minns, P. Piseri, D.M.P. Holland, Kevin C. Prince, Davide Faccialà, Bruno Nunes Cabral Tenorio, M. Bonanomi, Sonia Coriani, Jacob Pedersen, R. Feifel, Alberto Simoncig, Alexander Demidovich, Carlo Callegari, Alexander Darius Brynes, Henry J. Thompson
article en
1 citations

Abstract

Tracking the multifarious ultrafast electronic and structural changes occurring in a molecule during a photochemical transformation is a challenging endeavor that benefits from recent experimental and computational progress in time-resolved techniques. Measurements of valence electronic states, which provide a global picture of the bonding structure of the molecule, and core electronic states, which provide insight into the local environment, traditionally require different approaches and are often studied separately. Here, we demonstrate that X-ray pulses from a seeded free-electron laser (FEL) enable the measurement of high-resolution, time-resolved X-ray photoelectron spectra (XPS) that capture weak satellite states resulting from shake-down processes in a valence-excited molecule. This approach effectively combines the advantages of both valence- and core-state investigations. We applied this method to investigate photoexcited CS<sub>2</sub> molecules, where the role of internal conversion (IC) and intersystem crossing (ISC) in determining the predissociation dynamics is controversial. We present XPS spectra from photoexcited CS<sub>2</sub>, obtained at the FERMI FEL. High-resolution measurements, compared to the corresponding spectra obtained from accurate multireference quantum chemical calculations, reveal that shake-down satellite channels are highly sensitive to both valence electronic and geometric changes. Previous studies of the predissociation dynamics have led to uncertain assignments of the branching between singlet and triplet excited states. We derive a propensity rule that demonstrates the spin-selectivity of the shake-downs. This selectivity allows us to unequivocally assign contributions from the bright and dark singlet excited states, with populations tracked along the predissociation dynamic pathway.

Journal of the American Chemical SocietyVol. 147(36)
Mott MacDonald (United Kingdom) (GB), University of Trieste (IT), University of Ottawa (CA), Universität Hamburg (DE), Science and Technology Facilities Council (GB), University of Milan (IT), Kansas State University (US), Norwegian University of Science and Technology (NO), Charles University (CZ), AREA Science Park (IT), Deutsches Elektronen-Synchrotron DESY (DE), SLAC National Accelerator Laboratory (US), Daresbury Laboratory (GB), Elettra-Sincrotrone Trieste S.C.p.A. (IT), University of California System (US), Istituto Officina dei Materiali (IT), Institute of Structure of Matter (IT), Probiotical (Italy) (IT), Plasma Technology (United States) (US), Istituto di Fotonica e Nanotecnologie (IT), Linac Coherent Light Source (US), Science and Technology on Surface Physics and Chemistry Laboratory (CN), Center for Free-Electron Laser Science (DE), National Research Council Canada (CA), University of Southampton (GB), University of California, Davis (US), University of Gothenburg (SE), Science and Engineering Research Council (SG), Politecnico di Milano (IT), Technical University of Denmark (DK)
Leverhulme Trust, University of Southampton, Knut och Alice Wallenbergs Stiftelse, Vetenskapsrådet, Novo Nordisk Fonden, Engineering and Physical Sciences Research Council, Science and Technology Facilities Council, Division of Physics, Basic Energy Sciences
Openalex Percentile: Top 28%
Electron and X-Ray Spectroscopy Techniques
0.66
DOIOpen Access PDFOpenAlex
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