Phenomenology of electron solvation in polar fluids

The phenomenology of electron solvation in polar solvents is studied by investigating the characteristics of electron solvation in a model polar solvent, a Stockmayer liquid characterized by a combination of Lennard-Jones and dipolar intermolecular interactions which interacts with the electron with a combination of short range repulsive and of electrostatic (dipole-charge) interactions. Energetics and dynamical properties of the solvated electron are studied as functions of the solvent density and of solvent molecular parameters which determine the electron solvent interaction and the solvent dynamical response. We find that electron localization in this solvent is caused primarily by the repulsive part of the electron-solvent interaction. Upon increasing the solvent molecular dipole from zero, the electron becomes more localized; however, this effect seems to saturate at moderate solvent polarities, and further increase of the polarity changes the ground (and excited) state energies without affecting strongly the electron size. In this regime the electron behaves approximately Like a classical charge distribution as far as the dependence of its solvation energy on the solvent polarity is concerned. The dynamical response of the solvent to the solvated electron is investigated by studying the solvent-induced fluctuations of the electron's energy levels. As expected we find that fluctuations in the ground and excited state energies are dominated by the electrostatic part of the electron-solvent interaction, and their dynamics therefore reflects the solvent rotational motion. Surprisingly, however, the electrostatic contributions mostly cancel in the fluctuations of the gap between the ground and first excited state. Consequently the gap fluctuations are dominated by the solvent translational motions. The implications of these observations on the dynamics of electron solvation are discussed.