ELECTRON AND HEAVY-PARTICLE ENERGY REDISTRIBUTIONS IN GLOW-DISCHARGESIN GAS-MIXTURES

A review is presented on the contemporary modelling efforts describing the coupled electronic and heavy particle excited state kinetics in g low discharges in gas mixtures. The dramatic effects of the heterogene ous collisional interactions between the electronic/vibronic states of the gas mixture constituents on the dissociation, ionization, gas hea ting, discharge impedance and power loading are described and discusse d. A template construct of a collisional model of molecular gas mixtur es where the electron kinetics are obtained from the collisional Boltz mann transport equation, and the vibrational kinetics are governed by a system of vibrational master equations, is described in detail. Thre e test cases are discussed: (i) Ar- Cl-2, (ii) N-2 - O-2, and (iii) N- 2 - H-2. The generic guidelines that are derived from the analysis of the above mixtures are that: (a) There is a strong coupling between th e dissociation and the ionization balances in gas mixtures. It is caut ioned that for most conditions, even in pure molecular gases, neither channel can be studied independently of the other. (b) In molecular ga s mixtures, the heterogeneous collisional interactions between the met astable 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 inconsis tent and misleading conclusions on the throughput of these discharges.