On the possible role of the reaction H+H2O→H2+OH in the radiolysis of water at high temperatures

It is proposed that oxidation of water by the hydrogen atom may play an important role in the high-temperature radiolysis of water at low linear energy transfer (LET). The observed increase of the primary yield of H2, g(H2), in the radiolysis of water at high temperatures is shown to be consistent with the occurrence of the reaction H+H2O→H2+OH. The temperature dependence of the rate constant for this reaction has been determined by diffusion-kinetic modelling of spur processes in neutral water. Based on a rate constant of 0.086 M−1 s−1 at 25 °C estimated from thermodynamic data, and literature values of g(H2) as a function of temperature, a corresponding activation energy of 66.3±0.8 kJ mol−1 has been calculated over the temperature range 20-300 °C. The deterministic calculations also indicate the important role of the reaction eaq-+H2O→H+OH- in the production of the H atom at elevated temperatures in agreement with stochastic studies.