Kinetics of plasmachemical processes in the expanding flow of nitrogen plasma

Abstract

The extended state-to-state kinetic model, taking into account the possibility of the formation of non-Boltzmann distribution over the vibrational levels for different electronic states (X1Σ+g, A3Σ+u, B3Πg, a'1Σ−u and C3Πu) of N2 molecules in strongly nonequilibrium conditions, has been built. The numerical analysis of the processes in the expanding supersonic flow of primary equilibrium nitrogen plasma has demonstrated that disruption of thermodynamic equilibrium in a supersonic flow results in the formation of plateau type vibrational distribution both in the ground X1Σ+g and in the excited electronic states. It has been shown that the neglect of the disruption of thermodynamic equilibrium between vibronic states of N2 molecules and translational degrees of freedom can lead to significant errors in the populations of vibrational levels even in the ground state of the N2 molecule, as well as in the concentrations of charged species and in the electron and translational temperatures. The principal processes responsible for the formation of non-Boltzmann distribution over vibrational levels, both in the ground and in the excited electronic states of the N2 molecule, are carefully investigated. It is revealed that in the expanding supersonic flow of nitrogen plasma the population inversion at the (B3Πg,V ) → (A3Σ+u,V +n) transition with V >24 and n = 1, 2 can form.