Solute specific polar solvation studied by photon echo spectroscopy

Polar solvation dynamics of two solute molecules in a series of 1-alcohols has been studied using the three-pulse photon echo peak shift technique. The inertial dynamics, on sub-200 fs timescale, is essentially independent of solvent in the 1-alcohol series. For a given solute, the solvent dependence is mainly manifested in the diffusive solvation dynamics. The solute dependence appears as a significantly stronger inertial component in one of the molecules. We ascribe this solute dependence to the differences in charge redistribution upon excitation. A detailed investigation of oscillations of the peak shift reveals a solvent dependent beating that can be connected to solvation of the vibrational mode in the excited state. The solvent dependence of the dephasing dynamics of the excited state mode can be explained by the electronic transition frequency correlation function and the beating pattern of the echo signal originates from interference between ground and excited state Feynman pathways.