Ab initio Investigation of Br-3d Core-Excited States in HBr and HBr+ Toward XUV Probing of Photochemical Dynamics
Journal Article - Open Access
University of California Berkeley Berkeley United States
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Ultrafast X-rayXUV transient absorption spectroscopy is a powerful tool for real-time probing of chemical dynamics.Interpretation of the transient absorption spectra requires knowledge of core-excited potentials, which necessitates assistance from high-level electronic-structure computations. In this study, we investigate Br-3d core-excited electronic structures of hydrogen bromide HBr using spin-orbit general multiconfigurational quasidegenerate perturbation theory SO-GMC-QDPT.Potential energy curves and transition dipole moments are calculated from the Franck-Condon region to the asymptotic limit and used to construct core-to-valence absorption strengths for five electronic states of HBr and two electronic states of HBr. The results illustrate the capabilities of Br-3d edge probing to capture transitions of the electronic-state symmetry as well as nonadiabatic dissociation processes that evolve across avoided crossings. Furthermore, core-to-valence absorption spectra are simulated from the neutral state and the ionic states by numerically solving the time-dependent Schroedinger equation and exhibit excellent agreement with the experimental spectrum. The comprehensive and quantitative picture of the core-excited states obtained in this work allows for transparent analysis of the core-to-valence absorption signals, filling gaps in the theoretical understanding of the Br-3d transient absorption spectra.
- Radiation and Nuclear Chemistry
- Atomic and Molecular Physics and Spectroscopy