Structure of the aqueous electron.

Recently there has been a revival of interest in the basic structure of the aqueous or "hydrated" electron, e-(aq). According to the conventional picture, this species occupies a cavity or excluded volume in the structure of liquid water, with a characteristic absorption spectrum ascribable to s → p excitations of a particle in a quasi-spherical box. This traditional picture has been questioned over the past few years, however, on the basis of a one-electron pseudopotential model that predicts a more delocalized spin density and no distinct cavity. This Perspective reviews the known experimental properties of e-(aq) along with attempts to reproduce and understand them using both one-electron models and many-electron quantum chemistry calculations. The overwhelming weight of the evidence continues to support the conventional excluded-volume picture of the aqueous electron.