Spectroscopic Study on Vibrational Distribution of N₂ C³Π and B³Π States in Microwave Nitrogen Discharge

Abstract

We examined the vibrational and rotational temperatures of the C 3 Π and B 3 Π 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 ≈0.5–0.7 eV and T r ≈0.07–0.15 eV at B 3 Π ( v =7, 8 and 9), whereas T v ≈0.65–0.9 eV and T r ≈0.06–0.16 eV at C 3 Π ( v =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.