Abstract
Radiation of micro-air plasma-jets was measured at low pressure with high spatial resolution, and temperatures were estimated. Radiation measurement was made spectroscopically in the wavelength region of 200 to 900 nm. In the region of 280 to 480 nm, the bands of N_2^+ and N_2 molecules were predominant. Some atomic lines of N and O were observed in the infrared region of 700 to 900 nm. Temperatures of the plasma-jet were estimated with a spectral matching method for N_2^+ 1- bands and Boltzmann plot method for the atomic lines. Rotational temperatures were estimated 5,000 to 8,000 K, and vibrational temperatures 34,000 to 70,000 K, both with some axial variations. Electronic excitation temperatures of oxygen atomic lines were estimated 5,000 to 9,300 K. It was found that the rotational temperatures had large difference from the gas temperature based on an empirical formula for a supersonic free-jet, but decreased downstream in the expansion flow region, and also the vibrational temperatures were much higher than those expected.
