The nature of the precursors of radiolytic molecular hydrogen in water, and the mechanism of positronium formation in liquids

The dependence of H2 yields on the concentration of certain solutes indicates that molecular hydrogen is formed via recombination of its precursors in spurs. The order of efficiency of solutes in decreasing the formation of H2 does not correlate with the rate constants of their reactions with esub(aq)- or H. Due to their diffusive motion at energies <= 102 eV and to their comparatively long lifetimes in the subvibrational energy range at the end of their tracks, positrons may form postronium by a reaction with (epi)thermal electrons. The order of the reactivity of solutes towards the precursors of positronium is the same as that towards precursors of the molecular hydrogen yield and is in agreement with the order of their relative rate constants towards the non-solvated electron. It seems that the non-solvated electron takes part in the formation of positronium and of radiolytic H2. (author)