Variations of the gas temperature in He/N₂barrier discharges

Abstract

In order to obtain the gas temperature in the microdischarge areas and in the ambient gas of dielectric barrier discharges in helium/nitrogen mixtures we have studied the rotational temperature of the emission of molecular nitrogen ions. In these mixtures the excited state N+2(B 2Σ+u) is formed mainly by Penning ionization. We have calculated the rotational spectra of the transition N+2(B 2Σ+u→X 2Σg+) using a known reaction scheme for discharges in helium/nitrogen mixtures (Pouvesle et al 1982 J. Chem. Phys. 77 817) by averaging over the temporal variation of the gas temperature after the ignition of a microdischarge. We obtained this variation by solving the Navier-Stokes equations for this case. It is shown, that under our experimental conditions (pHe = 38.5-156 kPa, pN2 = 40-6000 Pa) the rotational population of the nitrogen ions corresponds to the equilibrium distribution at the temperature of the surrounding gas.