FORMATION AND RECOMBINATION OF H3O+ AND HYDROXIDE IN IRRADIATED WATER

Measurements of transient conductivity changes in aqueous solutions during and after irradiation with 15-MeV electron pulses were carried out to study the formation and recombination of hydrogen and hydroxide ions. The hydrogen ion yield is GH+ = 2.9 ± 0.2 (ions/100 eV), independent of the pulse dose and the pH between 5 and 9. On the basis of Ge- = 2.8, GOH- = 0.1. The apparent neutralization rate constant k(H++OH) varies between 4.4 × 1010 and 1.5 × 1011 M-1 sec-1, depending on pulse dose and pH. Lower rate constants were obtained by increasing the number of ions formed by radiation and also by decreasing the concentrations of ions present before irradiation. The experimental data, including those of other authors, are consistent with the hypothesis that H+ and OH- ions produced by radiation recombine more slowly than normal ions at equilibrium, possibly due to a different structure of their hydration shells. However, their mobilities must be the same as those of normal ions, according to experimental evidence. It was further found that N2O, but not H2O2, converts hydrated electrons into hydroxide ions within less than 0.2 μ sec. With H2O2, a negatively charged intermediate forms which has a half-life of 0.3 sec in alkaline solution.