The differences in the rotational temperatures between neutral molecules and molecular ions are examined for low-pressure microwave discharge nitrogen plasma and oxygen plasma. For N2 plasma, the rotational temperatures of the second positive system (2PS) and first negative system (1NS) are measured, whereas for O2 plasma, those of the atmospheric absorption band (A-band) and 1NS are measured for neutrals and ions, respectively. The experimentally measured spectra are compared with the theoretically calculated ones to determine the vibrational and rotational temperatures as best fitting parameters. It is found that the ions have a higher rotational temperature than neutrals for the N2 plasma, while both have almost the same temperature for the O2 plasma, for which a discussion is made on the basis of atomic and molecular processes. The difference in the rotational temperature between the neutrals and the ions is also discussed from the viewpoint of the atomic and molecular processes in the plasmas.

We measured rotational temperature of oxygen plasma by optical emission spectroscopy (OES) in order to examine approximate value of its gas temperature. We generated microwave discharge oxygen plasma in a cylindrical quartz tube whose inner diameter 26 mm with its discharge pressure 0.5 - 2.0 Torr. We measured the band spectrum of radiative transition A