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.