Ionization in the track of a high-energy electron in hydrocarbon liquids; study of positive and negative ion scavenging using nanosecond pulse radiolysis

Abstract

The lifetime distribution of the charged particles in the track of a high-energy electron in cyclohexane and isooctane has been considered. Results on the decay of biphenyl ions in solutions of biphenyl obtained by means of pulse radiolysis with nanosecond time resolution have been compared with lifetime distributions calculated from the concentration dependence of the steady state scavenging, using recently determined absolute rate constants for reaction of excess electrons and mobilities of the charged species. The discrepancy is relatively small for cyclohexane but large for isooctane. It is concluded that the scavengers considerably affect the initial spatial distribution of the charged species in the track. The kinetics of the reaction of the positive species in cyclohexane and isooctane with biphenyl, TMPD, and pyrene has been considered. It has been concluded that the mobile positive species in cyclohexane reacts with pyrene with a rate constant of 5×1011 mol−1⋅s−1, and has a lifetime of 50 ns. In isooctane no evidence for the existence of a mobile positive species has been obtained.