ON THE CONDITIONS NEEDED TO VERIFY A NONSTATIONARY DIFFUSION-MODEL BYKINETIC-ANALYSIS OF FAST FLUORESCENCE QUENCHING

Numerical experiments were carried out to test the feasibility of dist inguishing florescence quenching kinetics based on the treatment of Sm oluchowski, Collins and Kimball (SCK) from those showing single-expone ntial decays (Stern-Volmer kinetics) for a series of emission lifetime s lower than 1 ns corresponding to the measured lifetimes for seven th ioketones in perfluoro-1,3-dimethylcyclohexane as solvent. Experimenta l apparatus functions have been used to simulate the decays. The resul ts show that it is possible to determine the parameters of the SCK dec ay curve using appropriate equipment with short excitation sources and a detector with adequate time resolution and using the nonlinear leas t-squares fitting technique, provided the emission lifetime tau is lon ger than the duration of the nonstationary diffusion phase. Correlatio n coefficients are determined between the SCK function parameters, whi ch explain the difficulties often encountered in fitting decay curves to SCK theory. Parameter uncertainties have been estimated from a seri es of simulations which experimentalists can use to ensure the paramet ers, which they obtain from fitting fluorescence decay curves in the p resence quenchers, are valid and not interdependent.