Solvation and ionization near a dielectric surface

Solvation and ionization energies of ions and neutral atomic solutes near planar and spherical (cluster) surfaces were calculated using continuum dielectric theory. For highly polarized solvents, the magnitude of the solvation energy at the surface is similar to that in the bulk, while the reorganization energy and the photodetachment energy of an electron from a negative ion are found to be slightly larger for solutes located at the surface. The cluster size dependence of the solvation and ionization energies is found to be determined only by the properties of the solvent, in good agreement with experimental data, and to be insensitive to the location of the solute in the cluster. Implications for the size dependence of the photodetachment energies from negative ions in water and ammonia clusters are discussed. In particular it is suggested that the observed photodetachment energies from small (NH₃)_n^- clusters are compatible with the dielectric predictions for electron solvation in solid ammonia.