ENERGY-TRANSFER IN CONDENSED SYSTEMS - THE EFFECT OF PHASE ORGANIZATION

We investigate the effects that a phase transformation, from isotropic to orientationally (nematic) and positionally (smectic) ordered mesop hases, has on the energy transfer process between solute molecules. We combine Metropolis Monte Carlo simulations and a master equation appr oach to study radiationless energy transfer processes in three-dimensi onal ordered systems of identical uniaxial particles interacting via t he Gay-Berne potential. The time-dependent excitation probability and the fluorescence anisotropy decay curves show an enhanced energy trans fer in systems with a higher degree of order. We also find a non-isotr opic evolution of the time-dependent excitation probability in systems with positional as well as orientational order, with a faster energy transfer in the smectic planes. (C) 1997 Elsevier Science B.V.