Radiation and Temperature Characteristics of N2 Second Positive Bands of Microwave-Discharged Plasmas at Low Pressure

Abstract

Spectroscopic measurements of microwave-discharged low-pressure nitrogen plasmas were made in a tube with a diameter of 9.5 mm and length of 42 mm. Intense radiation of N 2 2+ bands and weak radiations of N 2 + 1−, N2 1+, and NO γ bands were observed. Unique intensity distribution of N2 2+ bands with high vibrational levels was observed as in the arc-discharged micro-air plasma-jets. Rotational and vibrational temperatures were determined by a spectral matching method with N 2 2+ (0, 2) and (1, 3) bands. The vibrational state of the plasma was also investigated by the N 2 2+ band intensity. As the experimental spectra could not be reconstructed by a usual equilibrium radiation theory with one rotational temperature, the theoretical spectra were constructed with the effects of predissociation and theoretical non-Boltzmann rotational population distribution, and were compared with the experimental ones. As a result, it was found that the vibrational and rotational temperatures were dependent on the theoretical model for ro-tational population distribution, that the rotational temperature was dependent on the vibrational states, and that the plasmas were in the vibrational non-equilibrium state. 5-9f $N @b L@ A(i, J)!' N 2 C 3 Π u ¿uBV$N i ////