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.

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The absorption spectrum observed on nanosecond pulse irradiation of triphenylmethyl chloride, 43CC1, solutions in cyclohexane results from the formation of three intermediates : the triphenylmethyl radical (absorption maximum 340 nm), the trityl cation (absorption maximum between 400 and 450nm) and a second positive ion species (absorption maximum 360nm). The free radical, formed by electron attachment to 43CCl with a rate constant of 3.7 x lo'* dm3 mol-I s-l, undergoes a reversible reaction with O2 for which the forward and backward rate constants are 1.2 x lo9 dm3 mol-1 s-' and 1 .Ox lo7 s-l, respectively at 20°C. In a mol dm-3 solution the trityl cation grows in over several hundred ns while over the same timescale the absorption at 360nm decays. The rate constant for reaction of the cyclohexane radical cation with $,CCl is 2.5 x 10" dm3 mol-' s-l. The initial product of this reaction, which is considered to be responsible for the 360 nm absorption, is thought to be the radical cation $3@Clf, which is converted to the trityl cation by further reaction with $,CCl with a rate constant of 5 k 2 x lo9 dm3 mol-l s-'. The trityl cation transfers its charge to TMPD with a rate constant of 8.7 x lo9 dm3 mol-' s-l.

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The pulse radiolysis of solutions of triphenylamine (TPA) in cyclohexane has been investigated using nanosecond time resolution. In addition to the transient absorption at 620 nm which has been previously observed in microsecond pulse radiolysis and which is assigned to the N-phenyldihydrocarbazole (DHC) derivative, the following species have been identified : singlet TPA, fluorescence maximum 365 nm, mean lifetime 4.5 ns ; triplet TPA, absorption maximum 520 nm, mean lifetime 38 ns ; triplet N-phenyldihydrocarbazole, absorption maximum 430 nm, mean lifetime 330 ns ; the TPA+ radical cation, absorption maximum 640 nm. The rate constants for the reaction of TPA', TPA3 and DHC3 with O2 have been measured to be 1.8 x lO'O, 1.3 x 10'O and 7 x lo9 M-' s-' respectively. For a lo-' M TPA solution the yield and decay kinetics of TPA+ ( E ~~~ = 14 000 M-' cm-l) are the same as'found for the biphenyl negative ion in a