CLASSICAL TRAJECTORY STUDIES VERSUS STATISTICAL-MODEL PREDICTIONS OF THE REAGENT ROTATIONAL ENERGY-DEPENDENCE FOR THE REACTION CL+ICH3-]CLI+CH3

The effect of reagent rotational excitation on the dynamics of the Cl+ICH3→ClI+CH3 reaction has been investigated using both the classical trajectory method and a statistical model, based on the RRK formalism, which incorporates angular momentum conservation. The reaction cross section calculated by the classical trajectory method is found to increase with reagent translational energy, which is consistent with both the experimental and microcanonical transition state results. The presence of a shallow well in the potential energy surface for Cl+ICH3 gives rise to collision dynamics with nearly symmetric product angular scattering, peaking in the forward direction, and the total energy available to the products being disposed almost equally into translation and internal excitation of the reaction products. Regardless of the initial translational energy, it is found that as the ICH3 rotational energy increases, the reaction cross section initially remains constant and then decreases. A similar behaviour is found when the statistical model is used and it is suggested that this negative dependence is a consequence of total angular momentum conservation. © 1990.