Spectroscopic study on vibrational distribution of N2C3Π and B3Π states in microwave nitrogen discharge

We examined the vibrational and rotational temperatures of the C-3 Pi and B-3 Pi states of N-2 by optical emission spectroscopy. We measured the band spectra (first and second positive systems) of N-2 compared the experimentally measured and the calculated spectra to determine the actual vibrational and rotational temperatures of the generated plasma.We generated a microwave discharge nitrogen plasma in a cylindrical quartz tube, (26 mm i.d.) with a discharge pressure of 0.5-1.0 Torr. The microwave frequency was 2.45 GHz and the output power was set at 600 W. It was found that T-v approximate to 0.5-0.7 eV and T-r approximate to 0.07-0.15 eV at B-3 Pi (nu = 7, 8 and 9), whereas T-v approximate to 0.65-0.9 eV and T-r approximate to 0.06-0.16 eV at C-3 Pi (nu = 0 and 1). We also discussed the measured vibrational populations using theoretical calculations, in which the variation in the number density was expressed in terms of molecular processes.