Theoretical Study of Indirect Photodissociation: Electronic Structure and Product Rovibrational Distributions of C sub 2 N sub 2 (C-Tilde Sup 1 PI/sub U/)

摘要

Polyatomic indirect photodissociation is treated as a quantum transition between quasidiscrete and dissociative (photofragment) states within a diabatic representation of the electronic Hamiltonian following a formalism developed by Kresin and Lester (KL). Relative product energy distributions are obtained from the evaluation of a multidimensional Franck-Condon overlap integral. The KL adiabatic method is followed to describe the nuclear dynamics of the dissociative state. The theory is applied to single-photon dissociation of C sub 2 N sub 2 (C-tilde sup 1 PI/sub u/) at 164, 158.7, and 153.6 nm to form CN(X sup 2 sigma sup + ) + CN(A sup 2 PI). Ab initio multiconfiguration Hartree-Fock (MCHF) excited state calculations are carried out to provide essential potential energy surface properties for the heavy-particle dynamics treatment. Product vibrational distributions are obtained in a collinear model and theoretical predictions are found to be in good agreement with recent experiments. An extension of the theory to 3-dimensions is described. Product rovibrational distributions and rotational temperatures are reported which take into account bending-vibrational modes and rotations employing only the adiabatic sudden limit of the general formalism of KL. 106 refs., 15 figs., 25 tabs. (ERA citation 13:003856)