a Study of Electron-Ion and Ion-Ion Recombination in Atmospheric Gas Discharges

In separate experiments, the electron-ion recombination rate, g(,ei), has been measured in CO(,2) and in mixtures of He, CO(,2), and N(,2); and the ion-ion recombination rate, (gamma)(,ii), has been measured in SF(,6) and in mixtures of SF(,6) and CH(,4). The rate constant was determined by analyzing the rising edge of the discharge current pulse. Measurements were made as functions of reduced electric field strength, gas pressure, and gas composition. In the electron-ion recombination study, (gamma)(,ei) in CO(,2) and in mixtures containing N(,2) and CO(,2) was pressure dependent. This dependence is interpreted as due to the separate effects of 2- and 3-body recombination processes. The results indicate that 3-body recombination is dominant at low field strengths for gas pressures above 1 atmosphere, whereas 2-body recombination is dominant at high field strengths. No pressure dependence was observed for mixtures containing He. In such mixtures, 2-body recombination is dominant. The addition of relatively low concentrations of He to the discharge leads to a dramatic change in the bulk recombination rate. Arguments are presented to explain the observation. In the ion-ion recombination study, (gamma)(,ii) was, in general, independent of pressure over the range of this study. (gamma)(,ii) was mixture dependent and decreased with increasing reduced electric field strength. When g(,ii) for the mixtures of SF(,6) and CH(,4) was plotted as a function of an effective ion temperature. T(,eff), it showed that for T(,eff) (GREATERTHEQ) 450(DEGREES)K, (gamma)(,ii) obeyed a simple power law. Arguments are presented to explain this behavior.