Role of solvent on vibrational energy transfer in solution

Abstract

ADVANCES in pulsed laser technology have made available ultra-short, tunable light pulses which permit the study of ultrafast energy-transfer processes within and between molecules. This information is essential for an understanding of chemical reactions on a molecular scale. Here we report results of a time-resolved study of the transfer of vibrational energy after excitation of the C–H stretch vibration in chloroform (CHCl₃) and bromoform (CHBr₃) dissolved in polar (deuterated acetone, CD₃COCD₃) and non-polar (carbon tetrachloride, CCl₄) solvents. We obtain quantitative information on the influence of the solvent on the rates of ultrafast intra- and intermolecular vibrational energy transfer. We find that the dipole–dipole interaction between an excited molecule and polar solvent molecules can lead to a strong acceleration of intramolecular energy-transfer processes. These results provide some insight into the way in which the rate of energy transfer and chemical reactivity are influenced by the polarity of the molecular environment.