Ion-ion recombination in mixtures of methane and sulphur hexafluoride

Abstract

We have measured the recombination rate for positive and negative ions in sulphur hexafluoride and in mixtures of methane and sulphur hexafluoride in an electron beam sustained discharge. Measurements were made as a function of gas composition, gas pressure in the range 100 to 600Torr, and reduced electric field strength in the range 12 to 150Td. When plotted as a function of an effective ion temperature, defined by the drift velocities of the ions in the applied electric field, the rates in each of the gas mixtures follow the same T;d.6 power law. From comparisons with theories appropriate to the recombination of positive ions with electrons it is suggested that the index of the power law might indicate that the recombination process follows an indirect path, with the approaching ions being initially trapped in stable orbits before final stabilisation of the collision.

Spatial distribution of radiation emitted by pulsed surface dielectric barrier discharge in air

“…The rate constant of the three-body ion-ion recombination (A8) also needs some correction. According to experimental data [29,30] the rate constant of this process in the presence of electric field is well approximated by the dependence…”

Synergistic effect in the rate of three-body ion - ion recombination in gas mixtures

“…inter-ionic interaction potential has a saddle point which decreases the probability that one ion captures another after a collision between the latter ion and an atom; this is controlled by the absolute value of E. The rate of process (28) has been measured as a function of E in CH 4 :SF 6 (Cornell and Littlewood 1987) and CH 4 :SF 6 :Ar and CH 4 :SF 6 :He (Littlewood 1990) mixtures. A Monte Carlo simulation by Littlewood and Pyle (1990b) has given the results which agree well with the available experimental data on the rate of process (28) in the CH 4 :SF 6 mixture versus E.…”

“…In the limit E → 0 Thomson's approach gives γ = 3 for the polarization ion-atom interaction (see, for instance, Bates 1985). Using another definition of the effective ion temperature Cornell and Littlewood (1987) and Littlewood (1990) have analysed the recombination rate measured in the CH 4 :SF 6 , CH 4 :SF 6 :He and CH 4 :SF 6 :Ar mixtures as a function of electric field and obtained γ = 1.6.…”

“…The pressure and temperature dependencies of the recombination rate in a pure gas are well understood. Although there are some investigations of the ion-ion recombination in gas mixtures (Cornell and Littlewood 1987, Littlewood and Pyle 1990a, Littlewood 1990), relatively little is known about the dependence of the rate of process (1) on the gas composition.…”