Computational analysis of the spatial distributions of low-energy electrons generated via water photolysis and photoinjection into electrodes in water

Abstract

Herein, we develop a dynamic Monte Carlo code for simulating physical processes occurring during electron transport and collisions in water. This code explicitly accounts for both collisions and Coulombic interactions when simulating the spatial distributions of low-energy electrons generated via liquid water ionization in two-photon laser excitation experiments. The consideration of the Coulombic field of the parent cation is a critical factor in these calculations. To verify the versatility of dmcc_phys, it is applied to replicate data obtained from contrastive experiments involving the ejection of low-energy electrons through photoinjection into electrodes in water, devoid of parent cations owing to electronic polarization. The calculations successfully reproduce both scenarios, demonstrating that our code, which integrates Monte Carlo and molecular dynamics methods, provides an advantage in simulating electron delocalization and relocalization into the parent cation compared with conventional Monte Carlo track-structure simulations, such as the particle and heavy ion transport code system and Geant4-DNA. Furthermore, we analyze the simulation results by fitting them against a combination of Gaussian and exponential distributions. Our findings indicate that electrons ejected by radiation depositing an energy of 11.9 eV distribute more extensively, resulting in a spur radius of 4 nm—larger than the 3 nm radius predicted using conventional methods. These capabilities enable precise estimation of the initial spur radius, a crucial parameter for predicting the time-dependent yields of hydrated electrons during the chemical stage.