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Title: A non-adiabatic dynamics study of octatetraene: The radiationless conversion from S{sub 2} to S{sub 1}

Simulation of the excited state dynamics of all-trans-1,3,5,7-octatetraene has been performed to investigate the ultrafast radiationless S{sub 2} → S{sub 1} internal conversion process. Multireference configuration interaction with single excitation method has been employed to optimize the equilibrium structure of the excited states, as well as the S{sub 2}/S{sub 1} conical intersection, and to investigate the non-adiabatic molecular dynamics of the S{sub 2}/S{sub 1} state transition. At the conical intersection, the molecule is found to be distorted from the original planar trans structure to a nearly perpendicular conformation around C{sub 3}−C{sub 4} bond, with the torsion angle being about 107°. Such structural change can result in mutual approaching of states S{sub 2} and S{sub 1} in energy, and drastically increase the nonadiabatic coupling between the two states by destroying the inter-state symmetry prohibition in the electronic wavefunctions. Surface-hopping molecular dynamics simulations are performed to describe the non-adiabatic process. Upon the Franck-Condon excitation to the S{sub 2} state, the molecule quickly twists its C{sub 3}−C{sub 4} bond and approaches the conical intersection region, where it can undergo efficient internal conversion to S{sub 1}. The decay time constant (τ) of S{sub 2} state is estimated to be around 251 fs by fittingmore » the occupation number of average fraction of trajectories using an exponential damping function. This value is reasonably consistent with previous experimental measurements of around 300–400 fs.« less
Authors:
;  [1]
  1. Institute of Theoretical and Computational Chemistry, Key Laboratory of Mesoscopic Chemistry of the Ministry of Education (MOE), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China)
Publication Date:
OSTI Identifier:
22253229
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 139; Journal Issue: 24; Other Information: (c) 2013 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; EXCITED STATES; INTERNAL CONVERSION; MOLECULAR DYNAMICS METHOD; SIMULATION; WAVE FUNCTIONS