Diffusive Transport of the Hydrated Electron: A Pseudoclassical Model

In order to elucidate the factors responsible for the enhanced diffusion rate of the hydrated electron compared to halide ions, a pseudoclassical simulation technique that mimics the adiabatic dynamical response of the electron is applied to halide-like ions in water for different solute-solvent potential models. Both the adiabatic and classical diffusive behavior are evaluated and compared to the quantum dynamics of the hydrated electron. It is shown that the adiabatic response per se is essential, but only partially responsible for the diffusion rate enhancement of the excess electron. Specific features of the solute-solvent interaction potential must also be taken into account for a realistic description of the electron mobility. These include the nature of the short range repulsion associated with the spatial confinement of the excess electron and the partial penetration of the excess electronic distribution into the first hydration shell. When these effects are also incorporated into the pseudoclassical model, both the solvated electron dynamics and solvation structure are closely reproduced by the model system.