Electronic excitation transport, diffusion and trapping

Abstract

Excitation energy transfer between donor (trypaflavine) and acceptor (rhodamine B, rhodamine 6G and cresyl violet) molecules randomly distributed in condensed phases is investigated using a time correlated single photon counting technique. The influence of excitation migration and translational diffusion is experimentally observed. The donor decay data demonstrate that fast diffusion/migration governs the decay kinetics in low viscosity solutions — the donor fluorescence decay being single exponential. The value of the diffusion coefficient calculated from decay curve analysis is almost a factor of five larger than the spatial diffusion constant and two orders of magnitude faster than the excitation migration transport constant. In high viscosity solvents efficient energy transfer follows the Förster dipole—dipole model.