Long-lived coherence in pentafluorobenzene as a probe of pi pi* - pi sigma* vibronic coupling

Huter, O., Sala, M., Neumann, H., Zhang, S., Studzinski, H., Egorova, D. and Temps, Friedrich (2016) Long-lived coherence in pentafluorobenzene as a probe of pi pi* - pi sigma* vibronic coupling Journal of Chemical Physics, 145 (1).

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The dynamics of pentafluorobenzene after femtosecond laser excitation to the optically bright pi pi* first excited electronic state have been investigated by femtosecond time-resolved time-of-flight mass spectrometry and femtosecond time-resolved photoelectron imaging spectroscopy. The observed temporal profiles exhibit a bi-exponential decay behavior with a superimposed, long-lived, large-amplitude oscillation with a frequency of nu(osc) = 78-74 cm(-1) and a damping time of tau(D) = 5-2 ps. On the basis of electronic structure and quantum dynamics calculations, the oscillations have been shown to arise due to vibronic coupling between the optically bright pi pi* state and the energetically close-lying optically dark pi sigma* state. The coupling leads to a pronounced double-well character of the lowest excited adiabatic potential energy surface along several out-of-plane modes of b(1) symmetry. The optical electronic excitation initiates periodic wavepacket motion along these modes. In the out-of-plane distorted molecular configuration, the excited state acquires substantial pi sigma* character, thus modulating the ionization probability. The photoelectron spectra and the anisotropy of their angular distribution confirm the periodically changing electronic character. The ionizing probe laser pulse directly maps the coupled electron-nuclear motion into the observed signal oscillations. Published by AIP Publishing.

Document Type: Article
Additional Information: Times Cited: 1 Hueter, O. Sala, M. Neumann, H. Zhang, S. Studzinski, H. Egorova, D. Temps, F.
Research affiliation: Kiel University
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
ISSN: 0021-9606
Projects: Future Ocean
Date Deposited: 12 Mar 2017 09:34
Last Modified: 12 Mar 2017 09:34
URI: http://eprints.uni-kiel.de/id/eprint/36148

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