On the temperature dependence of the primary yield and the product Gεmax of hydrated electrons in the low-LET radiolysis of liquid water

Monte-Carlo simulations are performed to calculate the temperature dependence of the primary hydrated electron yield (Ge aq - ) for liquid water irradiated by low linear-energy-transfer radiation (LET ~ 0.3 keV µm –1 ) in the range 25–325°C. Calculations are carried out by taking properly into account the effect of the time and temperature dependencies of the water dielectric constant on the electron–cation geminate recombination. Our computed Ge aq - values slightly increase with increasing temperature, in good agreement with experiment. The product Ge aq - ε max (e aq - ), estimated by using existing experimental data of the maximum molar extinction coefficient ε max (e aq - ), remains nearly constant or slightly increases, depending on the temperature dependence chosen for ε max . Our Ge aq - ε max (e aq - ) values compare generally well with most experimental data, as well as with the predictions of deterministic diffusion-kinetic model calculations. Moreover, our results indicate that the static dielectric constant of water (ε s ) does not play any significant role on the electron–cation recombination at early times. Such a finding is inconsistent with the interpretation, proposed by certain authors in the literature, that Ge aq - should in fact decrease as temperature is increased because of an increased electron–cation geminate recombination due to a lowering of ε s . Finally, the temperature dependence of the hydrated electron yields, calculated at various times between 10 ps and 1 µs, shows that at low LET, the time required to establish homogeneous chemistry in the bulk of the solution is ~10 –6 s in the range ~25–100°C, and that this time diminishes to ~10 –7 s at higher temperatures.