Dynamics of solvation in simple polar liquids is studied within the framework of the mean spherical approximation. Exact results are derived for the Born solvation energy and for the correlation function for the solvation time of an instantaneously formed ion (or dipole) in a polar solvent. The results are in qualitative agreement with the recent approximate treatment by P. Wolynes [J. Chem. Phys. 86, 5133 (1987)]. Implications of the results for the solvation dynamics of dipoles and of excess electrons in polar solvents are considered.

Ion and dipole solvation kinetics is studied within the framework of the mean-spherical approximation (MSA). The solvation dynamics in nonassociated polar solvents involves a hierarchy of relaxation times in accordance with Onsager's "inverted snowball" picture. The average solvation time is determined by the relative solvent and solute sizes and by the dynamic screening. The dipole solvation is slower than ion solvation due to the shorter spatial range of interaction. The theoretical results are confronted with experimental data on timeresolved fluorescence shifts of dipolar probe molecules in nonassociated polar solvents. The experimental kinetic data exhibit a crossover from a short-time dipole solvation behavior to ion solvation at intermediate and long times. For associated polar solvents the Onsager picture has to be modified to account for structure breaking in the first solvation shell(s).

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