Dynamic solvation. Ionic vibrations in non-stationary solvation shells

Abstract

In this paper we consider the nature of the interaction between the vibrations of the solvent shell and the vibrations of a solvated ion which is trapped inside that shell. The ionic vibrations have been considered elsewhere. The solvation shell vibrations are considered in a continuum representation which is a modification of the hydrodynamic treatment considered several years ago. Two specific vibrational modes of the solvation system are considered. The first is the volume non-conserving breathing mode. This mode is modelled as a density fluctuation. The second mode is a solvation surface mode of oscillation which is volume-conserving. Distortion of the solvation surface arises through the excitation of the surface modes. The coupling between the various modes of oscillation of the solvation shell and the ion are considered. In addition, Born–Oppenheimer levels of separation of the various degrees of freedom are discussed. Finally, the general form of the dynamical interaction between two solvated ions is derived.