Excited-state orientation-dependent irreversible interconversion and fluorescence depolarization in organized molecular media. I. Theory

Fluorescence depolarization in organized molecular media probed by the fluo rophores undergoing an excited-state orientation-dependent irreversible int er conversion is discussed. The effect of the angular dependence of the exc ited-state interconversion on the order parameters and correlation function s is examined in a systematic way by considering different angular dependen ce for the interconversion kinetic rate. The expected manifestation of this effect in the time-resolved fluorescence depolarization experiments is dis cussed on the basis of the synthetic decays for the experiments on membrane vesicles suspension and for variable-angle experiments on macroscopically ordered samples. The main properties of the model and its experimental appl ications are discussed. (C) 2001 American Institute of Physics.