Time-resolved excited-state triplet-triplet absorption spectra were measured for solutions of 2,5 diphenyloxazole (PPO) in various solvents, with the use of a pump and probe technique. The rate constants for intersystem crossing, triplet deactivation by oxygen, and triplet-triplet self-quenching are obtained. The latter two rate constants are substantially larger than the corresponding rate constants for 2-(1 naphthyl)-5-phenyloxazole-αNPO.
A. N. Dharamsi and Shawpin Jong, "Triplet-State Kinetics of 2,5 Diphenyloxazole (PPO)," Appl. Spectrosc. 42, 27-31 (1988)