Multireference Configuration Interaction Study of the Vibronic Transitions and Photodissociation of Vinyl Bromide and Vinyl Chloride Radical Cations in the Second Excited State

Recent development of techniques to obtain vibronically resolved spectra of radical cations of organic molecules provides detailed information regarding molecular structure and dynamics in the excited states that lead to photodissociation and/or ultrafast nonradiative decay through conical intersections. In this paper, the vibronic transitions and photodissociation of radical cations of vinyl bromide (CH2CHBr+) and vinyl chloride (CH2CHCl+) in the second excited state ((B) over tilde) are studied by multireference configuration interaction calculations. Vibronically resolved photofragment yield spectra for the ground state (X) over tilde-(B) over tilde transitions are analyzed using calculated Franck-Condon factors with optimized geometries and normal mode vectors for two states. The relevance of bond dissociation in the B state to the experimental spectra and the dynamics of the C2H3+ fragment is explored using calculated potential energy curves for the lower electronic states.