TRANSIENT EFFECT IN FLUORESCENCE QUENCHING INDUCED BY ELECTRON-TRANSFER .1. ANALYSIS BY THE COLLINS-KIMBALL MODEL OF DIFFUSION-CONTROLLED REACTIONS

Fluorescence quenching induced by electron transfer was studied by measuring the transient effect in decay curves and also the changes in stationary intensity with quencher concentration. The results were analyzed using the Collins-Kimball model of diffusion-controlled reactions, yielding the reaction radius R and the intrinsic rate constant k(ET) of electron transfer at the reaction radius. k(ET) values thus obtained are much larger than the rate of diffusion. R was found to increase with increasing-DELTAG of the electron transfer reaction. This is consistent with the prediction from the Marcus theory of electron transfer. The adequacy of the Collins-Kimball model in analyzing fluorescence quenching reaction is discussed.