SPATIAL PROPERTIES OF ENERGY TRANSPORT IN THREE DIMENSIONAL DISORDERED SYSTEMS

The picosecond transient grating technique is used to directly measure the excited state energy transport diffusion constant of dye molecules in solution. The use of extremely narrow grating fringe spacings (< 980A) enabled measurement of the excitation's spatial mobility from low concentration (C = 1) where the transport is non-diffusive up to concentrations (C‹≈10) where the transport is essentially diffusive. The results are compared to theortical predictions for the concentration dependence of the diffusive propagation of the excitation