Quantum efficiencies of fluorescence and one-photon dissociation of organic molecular vapors and their temperature dependences

In the temperature range 250–375°C, measurements were made of the quantum efficiencies of fluorescence and one-photon photodissociation of rarefied molecular vapors of paraterphenyl (p–TP) and 2,5-diphenyl-1,3,4,-oxadiazole (PPO) excited by λ=266 nm radiation and of 1,4-bis-[2-(5-phenyloxazolyl)]-benzene (POPOP) excited by λ=355 nm and λ=266 nm radiation. The quantum efficiency of photodissociation under the experimental conditions was only a small fraction of the total quantum efficiency of nonradiative deactivation of the fluorescence state of these molecules. The low fluorescence quantum efficiencies of p–TP and PPO (0.07–0.02) in the operating temperature range could be one of the reasons for the absence of laser action in vapors of these compounds.