Kinetics of fast reactions of charged intermediates in the pulse radiolysis of hydrocarbon solutions

The paper deals with the recombination of charged transients, generated in the pulse radiolysis of hydrocarbon solutions. If such liquids are irradiated with relatively high doses of ionizing radiation, the decay of the charged intermediates involves a considerable fraction of volume recombination. Therefore, the frequently used single ion pair concept fails in describing the experimentally observed concentration-time behaviour. Based on a diffusion kinetic approach a modified recombination model is suggested. It takes into account reactions between oppositely charged intermediates generated in different spurs. The time behaviour of monomer and dimer radical cations observed in the pulse radiolysis of styrene and styrene derivates in cyclohexane is described. In the case of low scavenger concentrations it is possible to simulate the observed time behaviour within homogeneous kinetics. If the scavenger concentration is above 0.01 mol dm-3 the inhomogeneous decay observed is described with a phenomenological model assuming single ion pair kinetics. (orig./BBR)