CONVERSION RATES AND ION MOBILITIES IN PURE NEON AND ARGON AFTERGLOW PLASMAS

Measurements have been made at room temperature of the rates of decay of the atomic ion species in afterglow plasmas in pure neon and argon at various pressures within the range 0·01-2 torr. In both gases, the variation of the measured decay rates with pressure, observed over about two orders of magnitude in pressure, is consistent with the loss of the atomic inert gas ions by diffusion to the plasma boundary and by conversion to molecular inert gas ions in three-body reactions with the neutral gas. The present measurements constitute the first observations of the three-body conversion process in argon by a method providing mass identification of the participating ion species. The values obtained for the rates of the conversion reaction in neon and in argon and for the reduced mobilities of the atomic inert gas ions in their pure parent gases are νNe+ = (99±5)po2s-1, νAr+ = (313±12)po2s-1 μNe + = 4.6±0.4 cm2 V-1s-1, μAr+ = 1.75±0.15) cm2 V-1s -1. These results are compared with the values which have been obtained by other workers and comparisons are also made with the existing theoretical estimates of the measured parameters.