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

Direct current N-2 flowing discharges were generated and conditions for the pink afterglow were obtained. Emissions from N-2(B, C) and N-2(+)(B) radiative 2 states were studied as a function of pressure, flow rate and post-discharge position. A one-dimensional kinetic model accounting for N-2(X, V), N-2(A, B, C, a, a', a"), N(S-4), N-1-4(+)(X) and N-2(+)(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, N-2(+)(B) ions and N-2(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 N-2(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.