Intermolecular vibrational relaxation in mixtures of benzophenone with noble gases

Special features of the collision transfer of vibrational energy in benzophenone vapors and its mixtures with foreign gases (He, Ar, Kr, and Xe) are studied from delayed luminescence (DL) upon laser excitation of benzophenone molecules to the singlet S-1 state. Variations in the intensities and decay rates of the fast and slow components of the DL with increasing pressure of vapors and foreign gases are analyzed. It is shown that processes of the establishment of the vibrational equilibrium (V-V relaxation) and thermalization of the vibrational energy (V-T relaxation) in polyatomic benzophenone molecules are separated in time and determine the decay rates of fast and slow components, respectively. The efficiencies beta of the exchange and vibrational energy transfer are estimated, as well as mean energies (Delta E) transferred during a collision. It is shown that upon the V-V exchange the values of beta and (Delta E) approach values that are typical for strong collisions and are comparable with those predicted by ergodic models of the collision transfer of the vibrational energy.