Electron and Heavy Particle Energy Redistributions in Glow Discharges in Gas Mixtures

Abstract

AbstractA review is presented on the contemporary modelling efforts describing the coupled electronic and heavy particle excited state kinetics in glow discharges in gas mixtures. The dramatic effects of the heterogeneous collisional interactions between the electronic/vibronic states of the gas mixture constituents on the dissociation, ionization, gas heating, discharge impedance and power loading are described and discussed. A template construct of a collisional model of molecular gas mixtures where the electron kinetics are obtained from the collisional Boltzmann transport equation, and the vibrational kinetics are governed by a system of vibrational master equations, is described in detail. Three test cases are discussed: (i) Ar − Cl2, (ii) N2 − O2, and (iii) N2 − H2. The generic guidelines that are derived from the analysis of the above mixtures are that: (a) There is a strong coupling between the dissociation and the ionization balances in gas mixtures. It is cautioned that for most conditions, even in pure molecular gases, neither channel can be studied independently of the other. (b) In molecular gas mixtures, the heterogeneous collisional interactions between the metastable excited electronic states play important roles in determining the discharge characteristics. (c) The calculations assuming constant E/N and constant electron density in gas mixtures can lead to inconsistent and misleading conclusions on the throughput of these discharges.