A model study of collision induced dissociation of a diatomic molecule by an atom

Abstract

The time-dependent Schrödinger equation for the collinear collision of an atom with a diatomic molecule is solved numerically after the manner of McCullough and Wyatt. The binding potential is taken to be a truncated square well and the interaction is impulsive (hard sphere). For the case in which all three masses are equal final relative momentum distributions and dissociation probabilities are obtained as a function of both the initial relative kinetic energy and the initial vibrational level. For purposes of comparison quasiclassical trajectory analyses of the same cases were performed. Quantum effects on collision-induced dissociation (CID) are seen to be important for this model. A very notable characteristic of the model, observed in both the quantum and classical results, yet not in most experimental results, is that CID is severely vibrationally inhibited, i.e., the probability of CID decreases as the initial vibrational quantum number increases at a fixed total collision energy. Probable causes of this strong vibrational inhibition are examined classically by a detailed trajectory analysis. It is concluded that the collinearity of the model is most likely responsible.