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Title: Long-lived coherence in pentafluorobenzene as a probe of ππ{sup *} – πσ{sup *} vibronic coupling

Abstract

The dynamics of pentafluorobenzene after femtosecond laser excitation to the optically bright ππ{sup *} 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 ν{sub osc} = 78–74 cm{sup −1} and a damping time of τ{sub 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 ππ{sup *} state and the energetically close-lying optically dark πσ{sup *} 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{sub 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 πσ{sup *} 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.

Authors:
; ; ; ;
Publication Date:
OSTI Identifier:
22675989
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 145; Journal Issue: 1; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-9606
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ANGULAR DISTRIBUTION; COUPLING; ELECTRONIC STRUCTURE; EXCITATION; EXCITED STATES; FLUORINE COMPOUNDS; MASS SPECTROSCOPY; MOLECULAR STRUCTURE; OSCILLATIONS; PHOTOELECTRON SPECTROSCOPY; POTENTIAL ENERGY

Citation Formats

Hüter, O., Sala, M., Neumann, H., Zhang, S., Studzinski, H., Egorova, D., E-mail: egorova@phc.uni-kiel.de, E-mail: temps@phc.uni-kiel.de, and Temps, F., E-mail: egorova@phc.uni-kiel.de, E-mail: temps@phc.uni-kiel.de. Long-lived coherence in pentafluorobenzene as a probe of ππ{sup *} – πσ{sup *} vibronic coupling. United States: N. p., 2016. Web. doi:10.1063/1.4954705.
Hüter, O., Sala, M., Neumann, H., Zhang, S., Studzinski, H., Egorova, D., E-mail: egorova@phc.uni-kiel.de, E-mail: temps@phc.uni-kiel.de, & Temps, F., E-mail: egorova@phc.uni-kiel.de, E-mail: temps@phc.uni-kiel.de. Long-lived coherence in pentafluorobenzene as a probe of ππ{sup *} – πσ{sup *} vibronic coupling. United States. doi:10.1063/1.4954705.
Hüter, O., Sala, M., Neumann, H., Zhang, S., Studzinski, H., Egorova, D., E-mail: egorova@phc.uni-kiel.de, E-mail: temps@phc.uni-kiel.de, and Temps, F., E-mail: egorova@phc.uni-kiel.de, E-mail: temps@phc.uni-kiel.de. Thu . "Long-lived coherence in pentafluorobenzene as a probe of ππ{sup *} – πσ{sup *} vibronic coupling". United States. doi:10.1063/1.4954705.
@article{osti_22675989,
title = {Long-lived coherence in pentafluorobenzene as a probe of ππ{sup *} – πσ{sup *} vibronic coupling},
author = {Hüter, O. and Sala, M. and Neumann, H. and Zhang, S. and Studzinski, H. and Egorova, D., E-mail: egorova@phc.uni-kiel.de, E-mail: temps@phc.uni-kiel.de and Temps, F., E-mail: egorova@phc.uni-kiel.de, E-mail: temps@phc.uni-kiel.de},
abstractNote = {The dynamics of pentafluorobenzene after femtosecond laser excitation to the optically bright ππ{sup *} 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 ν{sub osc} = 78–74 cm{sup −1} and a damping time of τ{sub 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 ππ{sup *} state and the energetically close-lying optically dark πσ{sup *} 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{sub 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 πσ{sup *} 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.},
doi = {10.1063/1.4954705},
journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = 1,
volume = 145,
place = {United States},
year = {2016},
month = {7}
}