Theory of Radiation Chemistry. II. Track Effects in Radiolysis of Water

A model is presented which describes the geometrical effects in the radiolysis of water as a result of the diffusion of free radicals. The motion of secondary electrons immediately following the passage of the ionizing particle is discussed in an appendix, and it is concluded that radicals are most likely formed in pairs at the approximate sites of the original ionizations. Models for the diffusion of these radicals are shown to result in a definite fraction of radicals which undergo initial recombination for gamma- and fast beta-rays, for which the spurs are considered as diffusing independently. For alpha-rays a connected-track model is used. For the intermediate case of tritium beta-rays, a two-stage model is constructed. In each case the comparative yields of the ``forward'' and ``radical'' reactions (GF and GR) are calculated. Subsequent chemical effects in pure water and solutions are also considered briefly.