Journal of Chemical Physics, Vol.109, No.21, 9494-9501, 1998
Vibrational relaxation of I-2 in complexing solvents : The role of solvent-solute attractive forces
Femtosecond transient absorption studies of I-2-arene complexes, with arene=hexamethylbenzene (HMB), mesitylene (MST), or m-xylene (mX), are used to investigate the effect of solvent-solute attractive forces upon the rate of vibrational relaxation in solution. Comparison of measurements on I-2-MST complexes in neat mesitylene and I2-MST complexes diluted in carbontetrachloride demonstrate that binary solvent-solute attractive forces control the rate of vibrational relaxation in this prototypical model of diatomic vibrational relaxation. The data obtained for different arenes demonstrate that the rate of I? relaxation increases with the magnitude of the h-arene attractive interaction. I-2-HMB relaxes much faster than I-2 in MST or mX. The results of these experiments are discussed in terms of both isolated binary collision and instantaneous normal mode models for vibrational relaxation.
Keywords:CHARGE-TRANSFER COMPLEX, TIME INTRAMOLECULAR DYNAMICS, BINARYCOLLISION THEORIES, POPULATION RELAXATION, LIQUIDS;PHOTODISSOCIATION, FLUIDS, RECOMBINATION, FEMTOSECOND, PHASE