Transient decay studies of photophysical processes in plastic scintillators

The photophysical behaviour of a variety of polymer and copolymer systems of potential importance in the field of plastic scintillator technology has been studied. In particular, polymers incorporating oxadiazole scintillator solutes as integral units of the polymer chain and polymers incorporating oxazole species have been examined. Unambiguous evidence, both steady-state and transient, for the formation of excimers between oxadiazole species is presented. The concept of a continuous distribution of excimer energies has been proposed. A number of scintillator solutes were dissolved in styrene and the changes in scintillation efficiency and lifetime measured during polymerization of the sample. It was not possible from these measurements to isolate and estimate the lifetime of the scintillator solutes, the complexity of the decays being too great. A semi-empirical approximation of the decay curves in terms of a triple exponential function is all that has been attempted. (author)