Stochastic simulation of the electron radiolysis of water and aqueous solutions

Stochastic modeling of the radiolysis of water and of aqueous solutions employing simulated track structures and the independent reaction times methodology is used to investigate the physical and chemical processes underlying observed radiation chemical kinetics. The calculations accurately reproduce both the time dependent yields of e_aq^- and the scavenging capacity dependence of the (scavenged) yields of e_aq^-, OH, H₂, and H₂O₂ measured experimentally. The local spatial distribution of e_aq^- is described by a Gaussian of standard deviation 4.0 nm. This distribution reflects the "thermalization" of the subexcitation electron. The value matches recent experimental estimates but is somewhat wider than predicted in earlier (deterministic) studies. The Gaussian distribution used for H₃O⁺, OH, H, and O has a standard deviation of 0.75 nm, which is of the same order obtained previously using deterministic methods. This distribution is due to the distance traveled between electronic collisions of low-energy (<25 eV) electrons and the fragmentation of the molecular cation, H₂O⁺.