Stochastic modelling of the influence of an applied electric field on the ion recombination kinetics of multiple-ion-pair spurs in low-permittivity liquids

Random-flights Monte Carlo simulation and stochastic master equation techniques are presented for modelling the influence of an applied electric field on the ion recombination kinetics in multiple-ion-pair spurs in low-dielectric-permittivity solvents. The calculated free-ion yield in two-, three- and four-ion-pair spurs with realistic initial spatial distributions increases linearly with the applied field strength for weak fields. The slope-to-intercept ratio predicted for the variation is numerically similar to that obtained analytically for a single ion pair as the escaping fraction of ion pairs is small and as the Fano factor is close to unity for low-dielectric-permittivity solvents. Consequently, for weak electric fields, it is predicted that experimental slope-to-intercept ratios for hydrocarbons will not provide any significant information about the spur-size distribution.