TY  - JOUR
AU  - Thompson, Henry J.
AU  - Bonanomi, Matteo
AU  - Pedersen, Jacob
AU  - Plekan, Oksana
AU  - Pal, Nitish
AU  - Grazioli, Cesare
AU  - Prince, Kevin C.
AU  - Tenorio, Bruno N. C.
AU  - Devetta, Michele
AU  - Faccialà, Davide
AU  - Vozzi, Caterina
AU  - Piseri, Paolo
AU  - Danailov, Miltcho B.
AU  - Demidovich, Alexander
AU  - Brynes, Alexander D.
AU  - Simoncig, Alberto
AU  - Zangrando, Marco
AU  - Coreno, Marcello
AU  - Feifel, Raimund
AU  - Squibb, Richard J.
AU  - Holland, David M. P.
AU  - Allum, Felix
AU  - Rolles, Daniel
AU  - Decleva, Piero
AU  - Schuurman, Michael S.
AU  - Forbes, Ruaridh
AU  - Coriani, Sonia
AU  - Callegari, Carlo
AU  - Minns, Russell S.
AU  - Di Fraia, Michele
TI  - Shake-Down Spectroscopy as State- and Site-Specific Probe of Ultrafast Chemical Dynamics
JO  - Journal of the American Chemical Society
VL  - 147
IS  - 36
SN  - 0002-7863
CY  - Washington, DC
PB  - ACS Publications
M1  - PUBDB-2025-04490
SP  - 32851 - 32860
PY  - 2025
N1  - CUI: Advanced Imaging of Matter
AB  - 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 CS2 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 CS2, 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.
LB  - PUB:(DE-HGF)16
DO  - DOI:10.1021/jacs.5c09162
UR  - https://bib-pubdb1.desy.de/record/639396
ER  -