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Title: Electron dynamics upon ionization: Control of the timescale through chemical substitution and effect of nuclear motion

Photoionization can generate a non-stationary electronic state, which leads to coupled electron-nuclear dynamics in molecules. In this article, we choose benzene cation as a prototype because vertical ionization of the neutral species leads to a Jahn-Teller degeneracy between ground and first excited states of the cation. Starting with equal populations of ground and first excited states, there is no electron dynamics in this case. However, if we add methyl substituents that break symmetry but do not radically alter the electronic structure, we see charge migration: oscillations in the spin density that we can correlate with particular localized electronic structures, with a period depending on the gap between the states initially populated. We have also investigated the effect of nuclear motion on electron dynamics using a complete active space self-consistent field (CASSCF) implementation of the Ehrenfest method, most previous theoretical studies of electron dynamics having been carried out with fixed nuclei. In toluene cation for instance, simulations where the nuclei are allowed to move show significant differences in the electron dynamics after 3 fs, compared to simulations with fixed nuclei.
Authors:
; ;  [1] ;  [2]
  1. Department of Chemistry, Imperial College London, London SW7 2AZ (United Kingdom)
  2. Laboratoire CEISAM - UMR CNR 6230, Université de Nantes, 2 Rue de la Houssinière, BP 92208, 44322 Nantes Cedex 3 (France)
Publication Date:
OSTI Identifier:
22416203
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 9; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; BENZENE; CATIONS; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; DENSITY; ELECTRONIC STRUCTURE; ELECTRONS; EXCITED STATES; JAHN-TELLER EFFECT; MOLECULES; OSCILLATIONS; PHOTOIONIZATION; RADICALS; SELF-CONSISTENT FIELD; SPIN; TOLUENE