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

TL;DR

This paper introduces a Monte Carlo method to study how superthermal hydrogen atoms slow down and thermalize in hydrogen gas, with applications to astrophysical phenomena like PDRs and shocks.

Contribution

It presents a simple, reliable Monte Carlo approach incorporating background molecule thermal distribution to analyze hydrogen atom thermalization, advancing previous methods.

Findings

Calculated collision density plots for H atoms in H₂ gas.

Determined transport cross sections from experimental data.

Outlined astrophysical applications including reaction rate estimates.

Abstract

We propose a simple and reliable method to study the translational relaxation of 'hot' H atoms following their production by chemical mechanisms. The problem is relevant to PDR's, shocks, photospheres, atmospheric entry problems. We show that the thermalization of H atoms can be conveniently studied by a simple method and set the basis for further investigations. The method adopted is Monte Carlo method including the thermal distribution of background molecules. The transport cross section is determined by the inversion of transport data. Plots of the collisions density of H atoms in H$_{2}$ gas are calculated and discussed also in the context of simple theories. The application of the results to astrophysical problems is outlined including numerical results for the reaction H + H$_{2}$O $\rightarrow$ H$_{2}$ + OH.