New mechanism for H-2 formation in water

The formation of H-2 in the radiolysis of liquid water is more closely asso ciated with the nonhydrated electron or precursor to the hydrated electron than with the hydrated electron. Experiments with 5 MeV helium ions suggest that the principle mechanism for hydrogen formation is dissociative recomb ination of the water cation and the nonhydrated electron. The nonhydrated e lectron undergoing recombination does not appear to be in the lowest energy p-like state, but it probably has an excess energy of several eV, The seco nd-order recombination processes is very sensitive to the type of ionizing radiation leading to the observed variation in hydrogen yields. Furthermore , the relative mobility of the reactants through heterogeneous interfaces m ay result in a substantial yield of molecular hydrogen in practical situati ons involving adsorbed water.