An initial G value of hydrated electrons updated by a dynamic Monte Carlo simulation

Abstract

In the radiolysis of water vapour, we can easily categorise ionisation and electronic excitation; however, the ratio of ionisation and electronic excitation for liquid water remains uncertain. The ratio is intrinsically related to the kind of radiolytic species generated. The complexity of subsequently induced DNA damage in a living cell exposed to radiation depends on the type of radiolytic species generated. To address this critical issue, we estimate the ratio of ionisation and electronic excitation from delocalised and localised components of secondary electrons respectively, using time-dependent simulation methods based on a Monte Carlo code and molecular dynamics. We also investigate the primary electron energy dependence of the ionisation (i.e., initial hydrated electron) yields after irradiation with 20 eV–30 keV electrons in liquid water. The estimated yields at 1 ps above 1 keV agree well with previous data in the literature, whilst those below 1 keV differ markedly from some conventional simulations. Generally, initial yields of hydrated electrons depend on the type of cross sections and branching ratios modelled, whilst our code provides initial yields based on femtosecond dynamics Monte Carlo simulations of secondary electrons, and will contribute significantly to various research fields involving water radiolysis.