Electron and heavy particle kinetics in a low-pressure nitrogen glow discharge

Abstract

A detailed kinetic model is used to investigate the mechanisms for ionization, dissociation and atomic re-association in a low-pressure positive column. The approach is based on the self-consistent solutions to the electron Boltzmann equation coupled to a system of rate balance equations for the levels, the electronically excited states of and the and ions. The maintenance electric field is self-consistently determined from the continuity equations for electrons and ions. The model provides a satisfactory explanation of measurements conducted in these conditions, in the range p = 0.6 - 2.5 Torr and I = 10 - 100 mA, for the reduced electric field and the concentrations of N atoms and and states. The rate coefficients and are derived here for the two reactions leading to associative ionization by collisions between electronic metastables and , respectively. The dissociation due to the vibration - vibration (V - V) and vibration - translation (V - T) energy exchanges is shown to represent only a minor contribution for the total rate of dissociation, in opposition to previous studies, due to the effects of fast V - T exchanges associated with - N collisions. Finally, it is shown that the reaction does not constitute an effective depopulating mechanism of N atoms as most of the N atoms so created are reconverted to the N by collisions on the wall and quenching.