Excitation temperatures in the ionizing plasma of high-pressure mercury discharges

Abstract

The excitation temperatures of mercury as well as the electron and gas temperature in two high-pressure pure-Hg discharges operated on ac have been determined by measuring the ground- and excited-state densities. The excitation temperature depends on the excited-state energy, is significantly lower than the electron temperature, and higher than the gas temperature. The differences in the temperatures are higher at the maximum current phase and for the lower pressure discharge. Comparison with the Saha densities shows that the plasma at the maximum current is in ionizing phase, whereas it is close to local thermodynamic equilibrium at the voltage zero crossing.