Kinetics of atoms, metastable, radiative and ionic species in the nitrogen pink afterglow

Abstract

Direct current N2 flowing discharges were generated and conditions for the pink afterglow were obtained. Emissions from N2(B, C) and N2+(B) radiative states were studied as a function of pressure, flow rate and post-discharge position. A one-dimensional kinetic model accounting for N2(X, v), N2( A, B, C, a, a', a''), N(4S), N1-4+(X) and N2+(B) species has been developed in order to describe the experimental observations. The analysis on the complete set of processes assumed in this paper has provided possible generation mechanisms for N atoms, N2+(B) ions and N2(B, C) electronically excited states as well as for metastable ones. It has been shown that ionization, excitation and dissociation processes occur simultaneously at the post-discharge region when the vibrational distribution function of N2(X, v) states heats as resulting from the efficient V-V pumping mechanism, which is very sensitive to pressure conditions. Here, the pink afterglow is described as a non-equilibrium plasma, i.e. ambipolar diffusion for ions and the condition of charge neutrality are assumed.