Nonequilibrium velocity distributions and recombination rates in electron–ion and ion–ion recombinations in weakly ionized gases

Abstract

The nonequilibrium velocity distributions and recombination rates in electron–ion and ion–ion recombinations in a heat bath of neutral molecules are investigated by solving the Boltzmann equation with the Monte Carlo simulation. The explicit time-dependent velocity distributions and recombination rates from the initial equilibrium to quasisteady states are obtained for the typical electron–ion dissociative recombination e+N+2→N+N in the heat bath of N2 and for the typical ion–ion recombination H++H− →H+H in the heat bath of H2. The velocity distributions and the recombination rates indicate significant deviations from equilibrium. The decreases in the recombination rates from the equilibrium rates are 30% for e+N+2→N+N and 15% for H++H−→H+H at quasisteady states for the heat bath temperature 300 °K and the charge concentrations X∼10−4 and 10−2, respectively. The Monte Carlo result is compared with the Chapman–Enskog solution by Shizgal and Karplus for H++H−→H+H. The Chapman–Enskog solution indicates a too large nonequilibrium for high charge concentration X≳10−4.