ELECTRON-MOBILITY IN A WEAKLY IONIZED SODIUM INERT-GAS PLASMA

dA parametrical study of the electron energy distribution function and electron mobility in a sodium-inert gas mixture is carried out. The c onditions are considered under which, due to the interaction between e lectrons and excited sodium atoms via collisions of the second kind, t he average electron energy exceeds the temperature of the neutral gas. In order to find the electron energy distribution function, the kinet ic Boltzmann equation is solved numerically. The electron mobility in Na-He mixtures is shown to be close to that for the Maxwellian electro n energy distribution function with the temperature determined from th e energy balance. It is shown that, in Na-Ar mixtures, the dependence of the mobility on the composition of the mixture, the degree of ioniz ation, and the population of the resonantly excited states of Na atoms is fairly complicated when the electron energy distribution function is nonequilibrium. The nonmonotonic dependence of the mobility on the above parameters is related to the Ramsauer minimum in the cross secti on for elastic collisions with Ar atoms. An anomalously low conductivi ty of the photoplasma in the Na-Ar mixture, which was previously obser ved experimentally, is explained by the nonequilibrium character of th e electron energy distribution function.