Photodissociation is one of the most important photoinduced chemical reactions. It occurs when the potential energy curve along a chemical bond is repulsive in an excited state. Typically, “ballistic” ultrafast dissociation leads to the broadening of absorption resonances and the smearing out of vibrational fine-structure. We report on the photodissociation of in the electronic state, characterized by a configuration, which can be reached via resonant inelastic x-ray scattering or direct ultraviolet absorption. In both cases the spectra show narrow vibrational resonances, in spite of the dissociative character of the state. We find that “delayed” dissociation pathways, caused by reflection of the nuclear wave packet, are responsible for this effect. In spite of the analogous topology of the potential energy surfaces of the core- and valence-excited states, the reflection of the wave packet takes place only in the latter. The two-dimensional wave packet of the O-H stretching coordinates becomes trapped in a “cavity” near the Franck-Condon region, resulting from a mismatch between the OH vibrational frequency in the cavity and the one at the dissociation limit.
- Received 9 November 2023
- Revised 24 April 2024
- Accepted 29 July 2024
DOI:https://doi.org/10.1103/PhysRevA.110.033119
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Atomic, Molecular & Optical
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