Electron thermalization in gases. IV. Relaxation time in molecular hydrogen

Theory of electron thermalization derived earlier by the author for rare gases [J. Chem. Phys. 72, 1657, 6289 (1980)] is extended to molecular gases, taking into account inelastic processes. Both direct and inverse collisions are considered, with due regard to microscopic reversibility and detailed balancing. After developing the general equations, specific application is made to molecular hydrogen in the long-time limit. Thus, relaxation times for electron thermalization are reported in H2 at different temperatures over the interval 20–1000 K. Analysis of relative contributions of elastic scattering, rotational, and vibrational processes to the relaxation time shows that these are temperature dependent. As such, sequences of collision processes in decreasing order of importance to the thermalization phenomenon are presented at several temperatures. Comparison with an experiment shows reasonable agreement.