Study of the excitation mechanisms of the second positive system in the negative glow of a N2-Ar discharge

In an Ar-N-2 discharge, the high excitation transfer from Ar(P-3(2,0)) to N-2 produces an overpopulation of the high rotational levels of the bands of the second positive system (SPS), and so the spectra interpretation is not straightforward. This paper presents a fit function for the SPS bands measured in Ar-N-2, which allows us to study the excitation process contributions to the N-2(C) level. The procedure was tested in the negative glow of a pulsed Ar-N-2 discharge at a pressure of 2.5 Torr, for different mixture concentrations. In this discharge, through the fitting, it was possible to calculate the variation of the N-2(C) densities produced by different excitation processes as well as the variation of Ar metastable density.