TEST OF A MODEL FOR REVERSIBLE EXCIMER KINETICS - PYRENE IN CYCLOHEXANOL

A model for reversible monomer-excimer kinetics that considers the time dependence of the excimer formation rate coefficient is proposed and tested for pyrene in cyclohexanol from 25 up to 85-degrees-C. Simultaneous analysis of the monomer and excimer experimental decay curves allows the determination of all the relevant parameters for this reaction. The diffusion coefficient follows an Arrhenius plot with activation energy of 36 +/- 1 KJ mol-1, the encounter radius varies between 7.3 and 8.9 angstrom, and the intrinsic rate constant for excimer formation varies between 2.4 x 10(9) and 1.1 x 10(10) M-1 s-1. The intrinsic reciprocal lifetime of the excimer follows an Arrhenius plot with activation energy of 12 +/- 1 KJ mol-1, and the rate constant for excimer dissociation, determined for high temperatures (T > 55-degrees-C) when reversibility is important, has different values depending whether geminate pair effects are considered or not in the analysis. The binding energy of pyrene excimer obtained considering pair effects (DELTA-H = 32 +/- 2 KJ mol-1) agrees with the published values for nonviscous solvents.