The dynamics of vibrational energy relaxation and bimolecular reactions in solution

Transient electronic absorption spectroscopy monitors the population of intermediate states in the vibrational relaxation of the iodo-substituted methanes, CHI₃, CH₂I₂, and CH₃I, in solution after excitation of the fundamental C-H stretching vibration. These experiments give times for both intra- and intermolecular energy flow for each molecule. The trend in intermolecular vibrational energy redistribution (IVR) times shows that the local vibrational state structure around the initially prepared states in each molecule, not the overall state density, controls IVR. Comparison of experiments in the solvents chloroform and acetone reveals the solvent role in IVR and shows a strong solvent effect on the intermolecular energy transfer (IET).; Two methods for mid-infrared wavelength generation and an infrared detection apparatus are among the technical advances toward vibrationally-mediated chemistry in solution. We discuss the feasibility of driving and controlling bimolecular reactions in solution, including proton transfer in hydrogen-bonded complexes and simple radical-molecule reactions. Current progress includes initiation of a bimolecular reaction and detection of accumulated products with sub-picosecond pulses. We also address our developments in overcoming the hurdles to the time-resolved version of this experiment.