A model for diffusion-mediated intramolecular fluorescence quenching based on the analytical solution of the Smoluchowski differential equation is considered. It is assumed that quenching occurs with a finite intrinsic rate at the distance of closest contact between the reactants. The solution has been worked out in terms of Laplace transforms with the aim to perform a deterministic identifiability study of this model. It is shown that the rate constant of excited-state deactivation and the system dimensionality can be uniquely recovered without additional information from a single fluorescence decay trace. The other system parameters (the diffusion coefficient, the intrinsic reaction rate constant, the distance of closest approach, and the distance of maximal separation), influencing the diffusion-controlled quenching, can be determined up to a scaling factor. However, if a priori information about one of these parameters is available, the model becomes globally identifiable (i.e., all model parameters can be uniquely determined). (C) 2000 American Institute of Physics. [S0021-9606(00)00211-7].