Time-dependent moment theory of hot-atom reactions

Abstract

A two-temperature moment method of solving the Boltzman equation is used to describe hot-atom relaxation and reaction. The moment equations are written in terms of standard kinetic-theory collision integrals and integrals over the reaction cross section. The theory is tested on a model system, and calculated hot yields are compared with Monte Carlo results. Convergence of the hot yield in increasing order of approximation is good for disparate masses of hot atoms and reservoir gas molecules, but severe difficulties occur with nearly equal masses (within a factor of about 3). A bimodal velocity distribution is introduced for these cases. The resulting moment equations give yields that are in much better agreement with the Monte Carlo calculations.