Dynamics of kinematically constrained bimolecular reactions having constant product recoil energy

Abstract

A model is presented for kinematically constrained reactions in which the product recoil energy is assumed constant (CPR approximation). It is further assumed that the reaction probability is independent of both the impact parameter and the collision energy for all collisions that lead to products. This model predicts that (1) the product vibrational distribution is bell-shaped, peaking at the vibrational level with an energy equal to the reaction exoergicity minus the product recoil energy, (2) small values of the impact parameters produce high vibrational excitation while large values produced low vibrational excitation, the specific opacity function for the most populated vibrational level being sharply peaked at the impact parameter equal to the equilibrium internuclear distance of the product diatomic, (3) the product rotational distribution for each vibrational level differs but has the form of a sharp leading edge for some J value followed by a falloff whose shape depends on the form of the collision energy distribution, and (4) the product average rotational energy associated with each vibrational level decreases linearly with increasing v to a value of v corresponding to the maximum in the vibrational distribution followed by a more slowly changing behavior. Comparisons are made of these predictions with some experiments on kinematically constrained bimolecular reactions. Some further extensions of the CPR model are suggested.