Evaluation of the electron energy distribution in a low-pressure Hg-Ar discharge with a two-temperature approximation

The low-pressure mercury-argon discharge was analyzed employing a two-temperature representation of the electron energy distribution. The electron energy distribution function was approximated with two Maxwellian portions, which represented a low-energy part of the electrons (bulk) characterized by higher temperature and a high-energy part of the electrons (tail) characterized by lower temperature. As a parameter representing non-Maxwellian distribution, the ratio of the tail temperature to the bulk temperature was introduced. The ratio was determined experimentally by adjusting the calculated field strength of the positive column to the observed one. The plasma parameters under the two-temperature approximation were shown to be obtainable by solving the rate equations for the particle densities and the energy balance equation for the whole electron group. The model was applied to the positive column of a 24-mm-diam tube. The rate coefficient of Hg 61S0 to Hg 61P1 transition was found to be 0.64 times that obtained under the Maxwell approximation.