Vibrational relaxation of I2I2 in complexing solvents: The role of solvent–solute attractive forces

Abstract

Femtosecond transient absorption studies of I2–areneI2–arene complexes, with arene=hexamethylbenzenearene=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 I2–MSTI2–MST complexes in neat mesitylene and I2–MSTI2–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 I2I2 relaxation increases with the magnitude of the I2–areneI2–arene attractive interaction. I2–HMBI2–HMB relaxes much faster than I2I2 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. © 1998 American Institute of Physics.