期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 117, 期 39, 页码 24069-24075出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.2015988117
关键词
X-ray stimulated Raman; conical intersections; vibronic coherences; ultrafast dynamics
资金
- US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences [DE-FG02-04ER15571]
- National Science Foundation [CHE-1953045]
- DOE
- Alexander von Humboldt Foundation through the Feodor Lynen program
- U.S. Department of Energy (DOE) [DE-FG02-04ER15571] Funding Source: U.S. Department of Energy (DOE)
The rates and outcomes of virtually all photophysical and photochemical processes are determined by conical intersections. These are regions of degeneracy between electronic states on the nuclear landscape of molecules where electrons and nuclei evolve on comparable timescales and thus become strongly coupled, enabling radiationless relaxation channels upon optical excitation. Due to their ultrafast nature and vast complexity, monitoring conical intersections experimentally is an open challenge. We present a simulation study on the ultrafast photorelaxation of uracil, based on a quantum description of the nuclei. We demonstrate an additional window into conical intersections obtained by recording the transient wavepacket coherence during this passage with an X-ray free-electron laser pulse. Two major findings are reported. First, we find that the vibronic coherence at the conical intersection lives for several hundred femtoseconds and can be measured during this entire time. Second, the time-dependent energy-splitting landscape of the participating vibrational and electronic states is directly extracted from Wigner spectrograms of the signal. These offer a physical picture of the quantum conical intersection pathways through visualizing their transient vibronic coherence distributions. The path of a nuclear wavepacket in the vicinity of the conical intersection is directly mapped by the proposed experiment.
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