Experimental comparison of rotational and gas kinetic temperatures in and He- discharges

Abstract

We report an experimental comparison of the rotational temperature and the gas kinetic temperature of and in a positive column discharge. The discharge is operated in an oven. The oven temperature, determined with a thermocouple, provides a lower bound for the gas kinetic temperature. An upper bound on the temperature is obtained by adding to the oven temperature a calculated increase in the gas temperature due to the discharge. The contribution of the discharge to the gas temperature is calculated under the assumption of complete conversion of input power into gas heating so that the estimate provides an upper bound. The rotational temperature of is determined directly with a Boltzmann plot of the first negative system. For , the ratio of the first minimum to the secondary maximum for the band profile of the second positive system is used to obtain the rotational temperature. We compare experimental spectra with simulated spectra generated under the assumption that the rotational temperature is equal to the minimum and maximum gas kinetic temperatures. The reliability of the rotational temperature as a gas temperature diagnostic under our experimental conditions is discussed for all bands investigated.