Radiative characteristics of n2 first positive band in visible and near-infrared regions for microwave-discharged nitrogen plasma

Abstract

The spectroscopic measurement of low-pressure microwave-discharged nitrogen plasma was conducted in the wavelength region of 550 to 1070 nm. Radiation from the N2 first positive band of the -v 14 0 to -v 14 4 band series and nitrogen atomic lines were observed. The experimental spectrum was compared with the theoretical spectrum, showing the effect of the predissociation of N2 B 3¬g state through N2 A0 5g + state and triplet splitting for the transition of 3¬ to the 3state. They agreed very well with each other for the -v 14 0 to -v 14 2 band series, which consisted of the lower vibrational levels of v0 14 0 to 7, but did not agree well for the higher vibrational levels of v0 14 8 to 12 in the -v 14 3 and +4 band series. By comparing the band head intensity of the experimental and theoretical spectra, the experimental vibrational population on each vibrational level for the B 3¬g state was estimated to be a non-Boltzmann distribution at the higher vibrational levels. In addition, the theoretical vibrational population distribution in the B 3¬g state was calculated using a master equation, and then agreement between the experimental spectrum and the theoretical spectrum with the non-Boltzmann distribution obtained from the master equation was improved.