Intermolecular Processes in Excited Electronic States in the Gas Phase (Review)

A brief review of works on the temperature dependences of the rate constants k_q of the intermolecular processes proceeding in the excited electronic states in the gas phase is given. The dependences k_q(T) for such biomolecular processes as intermolecular vibrational energy transfer in the triplet state vibrational quasi-continuum, triplet-triplet electron excitation energy transfer, and intermolecular photoinduced electron transfer have been compared. The experimental data have shown that in the gas phase for all analyzed intermolecular processes both an increase and a decrease in k_q with increasing temperature (T) is observed, which is not associated with the specific intermolecular interactions leading to the formation of long-lived components. The change in the type of temperature dependence is due to the change in the mechanisms of the radiationless transitions with increasing density of vibrational levels in the final electronic state. The applicability of the known models based on the theory of radiationless transitions for predicting the temperature dependences k_q(T) is discussed. __________ Translated from Zhurnal Prikladnoi Spektros-kopii, Vol. 72, No. 4, pp. 429–439, July–August, 2005.