Spectroscopic study on the vibrational populations of N2 C Π3 and B Π3 states in a microwave nitrogen discharge

Abstract

We measured the band spectra (first and second positive systems) of the nitrogen molecule to examine the vibrational and rotational temperatures of the C Π3 and B Π3 states by optical emission spectroscopy. We compared the experimentally measured and the calculated spectra to determine those temperatures of the generated plasma. We generated a microwave discharge nitrogen plasma in a cylindrical quartz tube (26 mm inside diameter) 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 Tv ≈0.5-0.7 eV and Tr ≈0.07-0.15 eV at B Π3 (v=7, 8, and 9), whereas Tv ≈0.65-0.9 eV and Tr ≈0.06-0.16 eV at C Π3 (v=0 and 1). Both rotational temperatures obtained from first and second positive systems were in good agreement. We also compared the measured vibrational populations with theoretical calculations, in which vibrational distribution function at N2 X and electron energy distribution function are calculated self-consistently. © 2007 American Institute of Physics.