Experimental study and modelling of a low-pressure N2-O2 time afterglow

The time afterglow of a pulsed discharge is used to investigate the neutral-particle kinetics in N-2-O-2 low-pressure mixtures. The pressure is in the range 0.5-2 Ton at 300 K and the mixture composition in the range 0-20% of oxygen. Time-resolved emission spectroscopy on N-2(B), N-2(C), NO(A) and NO(B) is employed to monitor energy transfers involving the metastable state N-2(A). The influence of N(S-4) and O(P-3) atoms on the kinetics is accurately treated using absolute concentration measurements by time-resolved absorption spectroscopy in the VUV range. It is shown that by an appropriate choice of the discharge repetition rate, the vibrational excitation of N-2(X) can be neglected. A chemical model, containing few unknown parameters, is developed in order to fit the experimental fluorescences. The NO(X) kinetics are investigated and its absolute concentration is deduced. Furthermore, it is shown that the N2(A) density is probably higher for pulsed discharges than for stationary low-pressure DC discharges.