Kinetics of nonequilibrium processes in air plasma formed behind shock waves: state-to-state consideration

A new kinetic thermal nonequilibrium model for air plasma, considering vibrations of N-2, O-2 and NO molecules in both the ground and electronically excited states in a state-to-state approach, was developed. The model treats in a consistent way the coupling of vibrational- electronic excitation of molecules and plasma chemical reactions as well as thermal nonequilibrium between translational degrees of freedom of electrons and heavy particles. The model was validated against the values of the radiation intensity of the NO (gamma) and N-2(+) (1-) bands measured in the shock-tube experiments in an O-2-N-2 mixture at shock wave speeds u(0) up to 9 km s(-1). Numerical analysis of thermally nonequilibrium processes in shock wave air plasma using the developed state-to-state model was conducted. It was shown that behind the shock front, a non-Boltzmann distribution over vibrational levels of N-2, O-2 and NO molecules in both the ground and electronically excited states forms, but at the same time low vibration levels of these molecules are still populated in line with the local Boltzmann distribution with its own vibrational temperature. However, at extremely high shock wave velocities (u(0) >= 8 km s(-1)) disruption of the Boltzmann distribution of O-2 (X-3 Sigma(-)(g)) and N-2 (X-1 Sigma(+)(g)) molecules starts from vibrational levels with quantum numbers V >= 2, so it is worth using the state-to-state consideration in such cases.