Collinear quasiclassical trajectory study of collision-induced dissociation on a model potential energy surface

Abstract

Quasiclassical trajectory calculations have been carried out at energies above the threshold for collision-induced dissociation for a model symmetric collinear atom–diatomic molecule system. Exact quantum mechanical calculations have shown that quasiclassical trajectories give a qualitatively correct picture of the dynamics in this system, in so far as reaction and total dissociation probabilities are concerned. Trajectories leading to dissociation are found to lie almost entirely in well-defined reactivity bands, with the exception of a few occurring in a small chattering region in which the outcome of the trajectory is extremely sensitive to its initial conditions. The energy distribution functions of the dissociated atoms are obtained and shown to vary substantially with initial conditions (reagent vibrational and translation energy). The form of these distributions is, to a major extent, determined by the position and width of the reactivity bands. The different dissociation reactivity bands are shown to be associated with different types of trajectories. Part of the vibrational enhancement of dissociation arises from the fact that the simplest possible trajectory leading to dissociation (one which crosses the symmetric stretch line only once prior to the onset of dissociation) is not obtained with ground state reagents.