Effect of intermolecular interactions on vibrational-energy transfer in the liquid phase

We present an experimental and theoretical study of the relaxation after excitation of the C–H stretch vibration for dilute solutions of CHCl3, CHBr3, and CHI3 dissolved in different solvents and for the pure liquids CHCl3 and CHBr3. Experimentally, we study the relaxation with pump–probe experiments using picosecond infrared pulses and we found that the vibrational-energy transfer takes place via an intramolecular vibrational-relaxation process followed by an intermolecular energy transfer. Theoretically, we develop a new model for the description of intramolecular vibrational energy transfer. In this model the important effects of the intermolecular interactions on the rate of intramolecular energy transfer are described. From the comparison between experiment and theory the relevant parameters for intramolecular vibrational-energy transfer can be identified.