Determination of excitation temperature and vibrational temperature of the N2(C 3Πu, ν′) state in Ne–N2 RF discharges

Abstract

Optical emission spectroscopy is used to investigate the effect of neon mixing on the excitation and vibrational temperatures of the second positive system in nitrogen plasma generated by a 13.56 MHz RF generator. The excitation temperature is determined from Ne I line intensities, using Boltzmann's plot. The overpopulation of the levels of the N2 (C 3Πu, ν′) states with neon mixing are monitored by measuring the emission intensities of the second positive system of nitrogen molecules. The vibrational temperature is calculated for the sequence Δν = −2, with the assumption that it follows Boltzmann's distribution. But due to overpopulation of levels, e.g. 1, 4, a linearization process was employed for such distributions allowing us to calculate the vibrational temperature of the N2 (C 3Πu, ν′) state. It is found that the excitation temperature as well as the vibrational temperature of the second positive system can be raised significantly by mixing neon with nitrogen plasma. It is also found that the vibrational temperature increases with power and pressure up to 0.5 mbar.