Ion Densities in Low Temperature Nitrogen Plasmas

Abstract

A cross-section library for the electron ionisation of hydrogen and nitrogen molecules, atoms and ions has been assembled and used for the derivation of reaction rate coefficients assuming a Maxwellian distribution of electron energies. For fixed electron temperatures, the steady-state and time-dependent ionisation of nitrogen molecules have been calculated for conditions relevant to glow discharge plasmas in which the dominant recombination mechanism occurs via the plasma-wall interaction. The analysis shows that there is a threshold electron temperature below which there is no steady-state ionisation. For a small range of temperatures above this threshold there are two possible ionisation states, but at higher temperatures only the more highly ionised state persists. The dependence of the ratio of N+ to N~ ions on filling pressure, confinement time and electron density is also discussed.