Monte Carlo calculation of the translational relaxation of superthermal H atoms in thermal H2 gas

Abstract

A simple and reliable method to study the translational relaxation of "hot" Hatoms following their production by chemical mechanisms is proposed. The problem is relevant to interstellar medium, shocks, photospheres, and atmospheric entry problems. It is shown that the thermalization of Hatoms can be conveniently studied by the Monte Carlo method, including the thermal distribution of background molecules, and sets the basis for further investigations. The transport cross section is determined by the inversion of transport data. The collision density of Hatoms in H2 gas is also calculated and discussed in the context of simple theories. The application of the results to astrophysical problems is outlined, including numerical results for the reaction H + H2O → H2 + OH. An approximate analytical formula for the reaction probability during Hatom thermalization is proposed. © 2012. The American Astronomical Society. All rights reserved.