TRIPLET EXCITATION-ENERGY TRANSFER AS A FUNCTION OF CONCENTRATION IN GLASSY METHYLBENZOPHENONE

Spectral diffusion following direct triplet excitation from the ground state in glassy Methylbenzophenone as a function of transition energy has been studied. The concentrations of donor and acceptor have been determined for different transition energies. The geometrical distribu tion was determined by a computer simulation. The cluster size increas es gradually with concentration and cluster percolation is observed at 0.31 mole fraction for a three dimensional system. The average distan ce between a donor and an acceptor also has been determined for differ ent concentrations. The energy transfer efficiency changes abruptly at a critical concentration of 0.054, corresponding to a critical distan ce of 9.8 Angstrom. The gamma value was evaluated to be 1.17.