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The carbon dioxide gas was injected into Ar induction thermal plasmas to investigate the plasma-quenching efficiency of CO2 and N2. In the experiments, C2 molecular band spectra and N+2 molecular spectra were found. Theoretical calculation of the radiation intensity for C2 Swan system and N+2 first negative system was carried out to study as functions of excitation temperature, rotational temperature and vibrational temperature. The fitting technique between the experimental and theoretical radiation intensities of the C2 Swan spectra and N+2 spectra was used for determination of rotational and vibrational temperatures. It was found that vibrational temperature was decreased with increasing CO2 admixture ratio into Ar thermal plasmas,which may be related with a decreased electron temperature. Figure 1 shows the spectra observed in 90%Ar-10%CO2 induction thermal plasma at atmospheric pressure at 40 mm below the coil end. We can see C2 Swan spectra with large intensity. By fitting the theoretically calculated C2 Swan spectra to this experimental spectra, we got vibrational temperature and rotational temperature of C2 molecules. Theoretical calculation was made on the assumption that excited populations of each excited levels including vibrational, rotational and electronic excitation levels follows the Boltzmann distribution with the specified temperatures. Figure 2 shows the radial distributions of vibrational and rotational temperatures of C2 molecules at 40 mm below the coil end. It can be seen that the vibrational temperature is around 6000–7000 K around the torch axis. On the other hand, the rotational temperature is around 4000–5000 K. This means there is non-equilibrium conditions in the Ar-CO2 induction plasma. In general the vibrational temperature is influenced by the electron temperature. On the other hand, the rotational temperature is close to heavy particle temperature. Thus, the experimental result in Fig. 2 shows the electron temperature is more than 2000 K greater than the heavy particle temperature even in the atmospheric-pressure plasmas. We also studied exitation,vibration and rotation temperatures for Ar-N2 induction thermal plasma. In this case, we calculated N+2 spectra and also Ar atomic line because these spectra is superimposed to each other. From the estimation of the these temperatures, we found that excitation temperature, vibrational temperature and Fig. 1. C2 spectra observed at 40 mm below the coil end in 90%Ar-10%CO2 induction thermal plasmas

Comparison of Vibrational-Rotational Temperature and Excitation Temperature in Ar-Molecular Gas Induction Thermal Plasmas