A deterministic identifiability analysis of kinetic models of a reversible intramolecular excited-state process involving species-dependent rotational Brownian diffusion is performed for spherical and cylindrically symmetric rotors. It is assumed that the axes of rotation do not change upon interconversion, and that the rate constants are independent of orientation. Use of three quencher concentrations allows the determination of two internally consistent sets of quenching rate constants, combinations of excited-state deactivation/exchange rate constants, individual rotational diffusion coefficients, relative orientations of transition moments, and restricted spectral information. Assignment of each set obtained to a particular species is not possible without additional prior information. (c) 2007 Elsevier B.V. All rights reserved.