Vibrational relaxation in the condensed phase is relevant to many aspects of chemistry, physics, and biology. It is involved in thermal chemistry, shock-induced chemistry, electron transfer, photochemistry, and biological processes such as vision and photosynthesis. Vibrationally excited solute molecules relax due to solvent-solute interactions; thus the rate of energy transfer is a probe of these interactions. We are investigating the role of the CH and OH stretch relaxation in a variety of systems in order to unravel the multiple relaxation pathways that are available to solute molecules and to develop the theoretical tools that will enable us to combine quantum descriptions of the solute with classical descriptions of the solvent.
In the above figure the energy levels of the title molecules are organized as a function of the difference in vibrational quanta between the initial OH(D) stretch state and the acceptor state. The bold (red) lines indicate the energy of the OH(D) stretch fundamentals. Significant acceptor states are shown in boxes. The box is wide for the neat methanol solution due to the strong hydrogen bonding interaction between solvent and solute. For relaxation of methanol and deuterated methanol in carbon tetrachloride, the coupling is weak and only nearly degenerate states are accessible. Comparing methanol with its deuterated analog one can see that the fast energy flow in CH3OD in CCl4 is due to near resonant Delta v=3 states. For references to our condensed phase work click on links below.