An analysis of molecular origin of vibrational energy transfer from solute to solvent based upon path integral influence functional theory

Abstract

Molecular process of vibrational energy relaxation of CN− ion in the aqueous solution has been investigated based upon path integral influence functional theory. In order to obtain a molecular-based picture, bath normal coordinates were retransformed to Cartesian coordinate, Eulerian coordinate, and intramolecular vibrational coordinate of the solvent molecule. Then, based upon this retransformation matrix, coupling of the solute with the normal modes may be assigned to the couplings with the solvent molecules. Further, with respect to two-phonon process which is dominant in the relaxation of the present system, the relaxation may be divided into single- and dual-molecular processes. We show that the single-molecular relaxation is dominant in the relaxation. Further, water molecules in the first hydration shell play an essential role in the relaxation, whereas the solvent molecules outside the first hydration shell make little contribution. The solvent molecules located in the direction of CN− bond axis were found to make great contribution to the relaxation.