Two-excited-state reversible reactions and fluorescence depolarization in uniaxially organized molecular media

The problem of fluorescence depolarization in uniaxially organized molecular media in the case of the fluorophores undergoing reversible excited-state reactions, is discussed. The two-ground- and two-excited-state species case is considered under the assumptions that the species-associated ground- and excited-state solute-matrix aligning interactions and the species-associated diffusion tensors are different. The state-to-state kinetic relaxation process is described in terms of rate constants which are independent of the angular orientations of the fluorophores within the aligned medium. Basic properties of the model are illustrated and discussed.