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

In an Ar-N2 discharge, the high excitation transfer from Ar(3P2,0) to N2 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-N2, which allows us to study the excitation process contributions to the N2(C) level. The procedure was tested in the negative glow of a pulsed Ar-N2 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 N2(C) densities produced by different excitation processes as well as the variation of Ar metastable density.