Theoretical models for solvated electrons

Abstract

This is a review of theoretical models that have been advanced to describe solvated electrons in disordered systems. The following four groups of models discussed: molecular orbital which includes dimer, tetramer and pentamer models; molecular field model; continuum model; dipole orientation model; and semicontinuum model. The CKJ and FFK semicontinuum model appears to be a reasonably successful theoretical model for treating the energy level structure of solvated electrons. It is particularly useful because it is simple enough to apply to a wide variety of solvent systems at different temperatures and pressures. It is successful at predicting many experimental trends. Nevertheless, the model has demonstrated defects both in the potential and in the wave functions used. The potential is too long range and the wave functions are too diffuse. It is necessary to use the ab initio semicontinuum model to study the geometrical structure of solvated electrons. Since good experimental data now exist for solvated electrons in, at least, water and ethanol with greatly contrasting geometries, it is possible to test the success of the ab initio model for treating geometry. However, the ab initio modification of the CKJ and FFK semicontinuum model makes it expensive and time consuming to apply.more » The semicontinuum model is notably unsuccessful in treating the optical absorption band shape. A number of other models have been proposed, some of which claim successful fits. In all cases it appears that some contribution from bound-continuum transitions must be invoked. This seems consistent with experiment. However, none of the theories have yet been able to give a clear physical basis for the observed line shape.« less