Optical emission spectroscopic measurements were performed on atmospheric pressure electrodeless microwave plasmas produced in a 95% carbon dioxide-5% hydrogen mixture. The rotational and vibrational temperatures of the plasma were determined by measuring the C2 Swan band spectra at wavelengths in the ranges of 500-517 and 548-565 nm. The electron number density of the plasma was deduced by measuring the Stark broadening of the hydrogen Balmer-β line shape at 486.13 nm. The microwave power was fixed at 2 kW, and the flow rate was varied from 5 to 20 standard liter per minute. The difference between the rotational and vibrational temperatures was found to be negligible. The temperatures reached 6200 (±200) K and were independent of the flow rate. The electron number densities of the plasmas were estimated to be approximately 2.06 (±0.12) × 1014cm-3. Thermodynamic-equilibrium calculations indicated that the temperature corresponding to the measured electron density was 6221 (±200) K, which is almost the same as the temperatures measured according to the C2 Swan band spectra. Therefore, the electron temperature was nearly the same as the gas temperature, and the plasma was in local thermal equilibrium.
- Carbon dioxide
- microwave plasmas
- optical emission spectroscopy
- stark broadening
ASJC Scopus subject areas
- Nuclear and High Energy Physics
- Condensed Matter Physics