Electron and vibrational kinetics in the hydrogen positive column

Abstract

The electron energy distribution function in H₂ and the vibrational distribution function of H₂(X, v) molecules have been self-consistently calculated for the typical operating conditions of a low-pressure, moderate current, hydrogen positive column by solving the Boltzmann equation together with a system of rate balance equations for the vibrational levels. This system takes into account e-V, V-V and V-T processes, the latter including both intermolecular and molecule-atom processes. The formulation provides a relationship between the characteristic vibrational temperature, T_v, the degree of ionisation, delta _e, the fractional concentration of dissociated atoms, delta _a, and the ratio of the electric field to the gas density, E/N. At low E/N the superelastic e-V collisions strongly enhance the high-energy tail of the electron energy distribution which results in a significant increase in the electron excitation rates, especially in the rate of dissociation by electron impact. The authors present calculations of electron transport parameters and excitation rates, of the power transfer by the electrons via the various collisional mechanisms, of the total power transferred to the translational and rotational modes by electron collisions and V-T and non-resonant V-V processes, and of the total dissociation rate.