EXCITATION-ENERGY DEPENDENCE OF INTRAMOLECULAR EXCIPLEX FORMATION AND ELECTRONIC RELAXATION IN THE COLLISION-FREE VAPOR

The excitation energy dependence of the intramolecular exciplex formation and the electronic relaxation has been studied in the collision-free vapor of 1-(9,10-dicyano-2-anthryl)-3-(pentamethylphenyl)propane. The fluorescence quantum yields and lifetimes of the 9,10-dicyanoanthyrl moiety and the aintramolecular exciplex in the collision-free vapor were observed to depend on the excitation energy within the S//1 absorption band. From the quantum yields and the decay rate constants, the excitation energy dependence of the association and dissociation rate constants of the intramolecular exciplex formation were determined. The assocation rate constant of the exciplex formation increases more remarkably with increasing excitation energy than the rate constants of 9,10-dicyanoanthyrl moiety and the exciplex. The excitation energy dependence of the association rate constant was discussed in terms of the nonradiative transition from the initial optical state to the final exciplex and the level density of the final state, which were calculated in the simple model system by means of the semi-classical mechanics.