Isotope Effects and Hydrogen Yields in the Radiolysis of H2O–D2O Mixtures at Very High Dose Rates

Abstract

Total hydrogen yields and their isotopic ratios have been measured in the single pulse, high dose rate radiolysis of H2O–D2O mixtures and acidic, basic, and nitrous oxide solutions. The yield from D2O is ~11% lower than in H2O at 7 × 1027 eV g−1s−1. In acid solutions the yields from H2O and D2O are the same within 5%. This yield, G(H2) = 1.15 ± 0.05 has been used to derive a value of kH+OH = 2.5 ± 0.3 × 1010 M−1 s−1.Using the literature values for primary yield data and for the reaction rate constants, values of α have been determined for the various hydrogen forming processes by computer calculation. We obtain values for hydrogen formation of αspur = 2.1 ± 0.1, αe+e = 6.0 ± 0.1, αH+H (effective) = 3.2 ± 0.1, and αe+H (effective) = 1.3 ± 0.2. Detailed consideration of the mechanisms involved suggest that there are little or no isotopic preferences in H + H and e + H reactions.