Comparison between Two Approaches to the Study of the Collision Dominated Electron Relaxation in Weakly Ionized Plasmas under the Action of an Electric Field

Recently it has been shown that in steady‐state situations under certain parameter conditions the conventional Boltzmann equation solution approach using the well known two‐term Legendre polynomial expansion fails to provide a sufficiently accurate description of the energy distribution and resulting macroscopic quantities of the electrons. Over the past few years, detailed studies of the temporal relaxation of electrons in a homogeneous, collision dominated, weakly ionized plasma have been performed using always the same approximation technique. Thus it is of particular interest to check the applicability of such a two‐term approximation to temporal relaxation processes by an independent approach without such limitation. An important improvement of Monte Carlo methods recently obtained allows to determine the energy distribution function far into the high energy range for steady‐state situations; further simulations of the non‐stationary evolution are now possible with high accuracy for a limited time period. Using these Monte Carlo techniques and the conventional approach we compared the energy distribution functions and some macroscopic quantities, in particular the excitation collision frequencies, in the inert gas plasmas of Ne and Ar for three selected cases of temporal relaxation. The results obtained with these two methods for different initial situations and for both inert gas plasmas with their very different atomic data show a very good agreement and thus confirm the validity of the two‐term approximation over the whole relaxation process for the considered cases.