Spectroscopic study of microwave plasmas of CO2and CO2–N2mixtures at atmospheric pressure

A comprehensive study of CO 2 and CO 2 (97%)–N 2 (3%) plasmas produced by a microwave torch at atmospheric pressure is carried out through the spectroscopic analysis of Abel inverted emission spectra. The temperature profiles at the exit of the cavity are determined from oxygen and carbon atomic line absolute intensities and from the adjustment of vibration–rotation molecular spectra. The predominant molecular radiation in the UV and visible ranges emanates from the C 2 Swan system in the case of CO 2 plasma and from CN violet and red systems for CO 2 –N 2 plasma. Significant contributions are also found from some O 2 , CO + and NO systems. A sensitivity analysis to rotational and vibrational temperatures is carried out systematically for the different investigated spectral ranges. It is found that the various molecular temperatures are very close to each other. However, atomic temperatures are slightly lower than molecular ones, indicating a weak departure from thermodynamic or chemical equilibrium for atoms.