ROLE OF SOLVENT ON VIBRATIONAL-ENERGY TRANSFER IN SOLUTION

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. © 1990 Nature Publishing Group.