Influence of CO2-laser mixture composition on the distribution of energy in nitrogen spectrum

Abstract

The DC glow discharge has been studied for mixtures of helium, nitrogen and carbon dioxide – these mixtures are widely used in CO2 lasers, which are classified as discharge lasers.Analysis of the bands of the nitrogen molecule (the first and the second positive system – B3Πg → A3Σg, C3Πu → B3Πg respectively) in an emission spectrum of the glow discharge was used to deduce an energetic balance and a vibrational temperature.The vibrational temperature of dinitrogen was determined by means of optical emission spectroscopy from the second positive system of the nitrogen molecule for various discharge currents and pressures. The dependence of the vibrational temperature on the nitrogen ratio in the mixture was also investigated.A connection between an occurrence of discharge instabilities (often called striations or ionization waves) and the composition of the gas mixture was observed – the less nitrogen was put in the mixture (in favor of helium), the larger part of positive column was subject to standing ionization waves. Ionization waves observed in the positive column of the glow discharge were investigated using optical emission spectroscopy, which showed sinusoidal profile of the vibrational temperature along the axial direction of the ionization waves.