The fluorescent intensity of solutions of diphenyloxazole (PPO) in cyclohexane is measured as a function of concentration for excitation by ggr; rays. The fluorescence spectrum of the solutions when excited byuvis also recorded. These uv measurements, together with the results of bgr; excitation, were used to examine the quenching influence of oxygen on the solute fluorescence and on the energy transfer from cyclohexane. The decay times of the solutions are measured. The results are interpreted to show: (1) a tendency of PPO to form molecular complexes in cyclohexane and (2) a ``static'' character for the oxygen quenching of cyclohexane. The dependence of transfer probability on solute concentration is discussed.
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