Non-equilibrium coupled kinetics in stationary N2-O2 discharges

Abstract

A detailed study of the coupled electron and heavy-particle kinetics in a low-pressure stationary N2-O2 discharge is carried out. The model is based on the self-consistent solutions to the Boltzmann equation coupled to the rate balance equations for the vibrationally excited molecules N2(X1 Sigma g+,v) and O2(X3 Sigma g-,v'), NO(X2 Pi r) molecules and N(4S) and O(3P) atoms. It is shown that the vibrational distribution of N2(X,v) plays a central role in the whole problem, affecting considerably the predicted concentrations of NO molecules and N atoms, whereas the concentration of O atoms is practically independent of both vibrational distributions. In particular, it is shown that, in the case of a rate coefficient of about 10-13 cm3 s-1 for the reaction N2(X,v)+O to NO+N, the N2(X,v) molecules are strongly de-excited by vibrational-translational energy exchange processes associated with N2-N collisions. In contrast, in the case of a higher value for this rate coefficient, the N2(X,v) molecules are efficiently destroyed by this mechanism. The contributions of the different processes to the total production of NO, N and O are evaluated and compared.