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.

Accurate molecular partition functions are required to determine both thermodynamic properties for equilibrium and nonequilibrium flow field calculations, and energy level populations for radiative heat transfer in high enthalpy flows, for instance. Thermodynamic functions of diatomic molecules are computed in this study at high temperatures and for nonequilibrium media in the framework of multitemperature models. Partition functions, average energies, and specific heats of N 2 , N + 2 , NO, O 2 , CN, C 2 , CO, and CO + are calculated up to 50,000 K by direct summation over energy levels using recent and accurate spectroscopic data and dissociation energy values. Estimates are made for the error introduced by neglecting the highest considered electronic states. For nonequilibrium media, the sensitivity of the multitemperature thermodynamic functions to different schemes for energy partitioning is discussed. In particular, the effects of vibration-rotation coupling are investigated. The tabulated results are available upon request.

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