Dielectric relaxation in aqueous alkali halide solutions due to hydration water exchange

Proceeding from a simple model for aqueous alkali halide solutions the effect of a finite residence time of the water molecules in the hydration layers of the ions on the dielectric relaxation behaviour is treated. The decrease of the static permittivity and the shift of the principal dielectric relaxation time with increasing electrolyte concentration are discussed. It is found that the mean residence times of the water molecules in the hydration layers of the ions are of the same order of magnitude as the molecular reorientation times.