Dissociation dynamics of collinear triatomic systems by the R-matrix method

Abstract

A straightforward computational technique is developed for the quantum mechanical study of unimolecular decay. It is applied to collinear triatomic systems in which the central atom interacts with one terminal atom through a harmonic oscillator potential and with the other terminal atom through a Morse oscillator potential. Stationary state wavefunctions for these systems are generated over an energy grid by applying the Wigner R‐matrix method with Buttle correction. Projections of the stationary wavefunctions onto nonstationary wavefunctions describing metastable states of the triatomic molecule are computed from the R‐matrix basis set expansion of these functions. Time dependent state‐to‐state transition probabilities and final product distributions are then calculated from the projections by Fourier transform and quadrature techniques. The observed time evolution is analyzed in terms of contributions from bound states, resonance states, and branch cuts. Rapid nonexponential decay observed for a variety of initial states is attributed to branch cut contributions to the time evolution.