Radiation chemical yield and mobility of electrons in liquid hydrocarbons

Abstract

Geminate ion-electron recombination is reconsidered theoretically and compared with the experimentally observed interdependence between free ion yield, G fi and electron mobility, μ or quasi-free electron energy, V 0. Thermal electrons are regarded as being formed in the quasi-free state, hence their motion can be described as that of a spherical wave with the geminate positive ion in the centre. One can show that the escape probability of thermal quasi-free electrons equals about one-half in each and any system if electron scattering by the molecules is neglected. Further, it is assumed that the escaped fraction of quasi-free electrons partially localize in the liquid. In this second stage of their life localized electrons behave as heavy particles in that they obey Onsager's recombination law. The distribution of distances between ions and localized electrons, an essential function in the Onsager theory, can be expressed in terms of trapping probability which is a function of either V 0 or μ. Calculated G fi( V 0) and G fi(μ) curves adequately agree with experiment. The last time that I had the chance of attending a lecture given by Robert L. Platzman was during the 4th International Congress of Radiation Research at Evian in 1970. Having been unable to read the text of that talk I have to rely on my memory in recalling the cardinal points of his arguments. So it is difficult for me to tell which ideas of the present paper stem directly from him. It is, however, beyond doubt that it was at his instigation, direct and indirect, that I decided to tackle the problems discussed below.