Fluctuation kinetics of the hopping fluorescence quenching in disordered solid solutions: A theoretical model and experimental evidence

Fluctuation kinetics of the hopping fluorescence quenching in disordered solid solutions is investigated for the first time. Measurements were made in the chelated complexes of rare-earth ions [Y_1−xTb_x(pyca)₃(H₂O)₂]nH₂O used as chromophore. The Tb³⁺ ions and the OH^--ions of unbounded water molecules appear as fluorescent donors and randomly distributed acceptors, respectively, with the dipole-dipole interaction between them. The measured fluctuation kinetics is the kinetics of the Förster type but with larger decay amplitude. It begins almost immediately after the initial static stage of quenching, and lasts for the entire interval of measurements leaving no room at all for the well-known exponential kinetics with constant rate. Proposed theoretical explanation of the phenomenon is based on the solution of the closed many-particle integral equation for the observable kinetics of hopping fluorescence quenching. The methods for determination of the energy transfer microparameters by the measured fluorescence quenching kinetics are discussed.