Optical emission spectroscopy of Ar-N2 mixture plasma

Optical emission spectroscopy measurements are presented to characterize the different excitation and ionization processes of both atomic and molecular species in Ar-N₂ mixture plasma under different discharge conditions. Particularly, the emission intensities of nitrogen (0-0) band of second positive system at 337.1 nm and (0-0) band of first negative systems at 391.4 nm are used to determine the dependence of their radiative states on argon fraction in the mixture. It is observed that the addition of argon gas influences the radiative states differently due to their different populating mechanisms. The results demonstrate that the addition of argon to nitrogen plasma remarkably enhance the population of N₂(C³Π_u) radiative state through Penning excitation involving argon metastable states. The electron temperature is determined from Ar-I spectral line intensities, using Boltzmann's plot method and is found to depend on argon fraction in the mixture.