Ultrafast solvation from Kerr relaxation and far-infrared spectroscopy in underdamped dipolar liquids

In this article, we report the results of our recent studies of underdamped solvation dynamics in the dipolar liquids. Previous theoretical studies of solvation dynamics in dipolar liquids have suffered from our lack of knowledge of the memory function or the dissipative kernel. Here, a reliable method to obtain this quantity directly from ultrafast spectroscopy is presented. This method can be extremely powerful as demonstrated by explicitly calculating the solvation energy time correlation function, S(t) for common dipolar liquids. For example, it is shown that the far infrared spectrum of liquid water and Kerr relaxation of liquid acetonitrile can be used to explain the dynamics of solvation of a newly created ion in the respective solvents. The calculated dynamics are in excellent agreement with the known facts. An advantage of the present scheme is that it offers a transparent interpretation of solvent involvement at the various stages of solvation