Photochemical control of energy transfer in molecular crystals

Abstract

Exposure of a 4,4′-dimethylbenzophenone single crystal at 4.2 K to radiation from a nitrogen laser causes chances in the phosphorescence spectrum and excitation energy transfer properties. The ratio of exciton to trap phosphorescence increases, the exciton phosphorescence decay, which is nonexponential initially, becomes more exponential, and a new luminescence origin appears above the exciton origin. These observations are interpreted in terms of photachemically produced scattering barriers that alter the exciton trapping rate, the exciton-exciton annihilation rate, and the energy transfer topology.