Isotope effects and hydrogen yields in the radiolysis of H2O-D2O mixtures at very high dose rates

Total hydrogen yields and their isotopic ratios have been measured in the single pulse, high dose rate radiolysis of H 2 O–D 2 O mixtures and acidic, basic, and nitrous oxide solutions. The yield from D 2 O is ~11% lower than in H 2 O at 7 × 10 27 eV g −1 s −1 . In acid solutions the yields from H 2 O and D 2 O are the same within 5%. This yield, G(H 2 ) = 1.15 ± 0.05 has been used to derive a value of k H+OH = 2.5 ± 0.3 × 10 10 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 α spur = 2.1 ± 0.1, α e+e = 6.0 ± 0.1, α H+H (effective) = 3.2 ± 0.1, and α e+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.