Ion-ion recombination in SF6 and in SF6-C2H6 mixtures for high values of E/N

Ion-ion recombination coefficients in a decaying SF6 plasma and in SF6-C2H6 mixtures are measured in the pressure range 15-90 Torr for reduced field strengths 100-250 Td. The charge composition is analysed and dominating ion-ion recombination channels in such plasmas are determined. Relations for estimating the potential drop at the electrodes are obtained for decaying plasma in strongly electronegative gases. The results of measurements are extrapolated for estimating the ion-ion recombination coefficient in SF6 for nearly critical field strengths. It is concluded that the ion-ion recombination should be taken into account in calculations of the discharge characteristics in non-chain reaction HF lasers.