Bleaching of vapors of lasing complex organic compounds

An investigation was made of the bleaching of vapors of the complex organic compounds 1,4–bi[2–(5–phenyloxazolyl)]benzene (POPOP) and 1,4–bi[2–(5–p–tolyloxazolyl)]benzene (TOPOT), which lase in the gas phase, induced by the action of second harmonic radiation from a Q-switched ruby laser. Using bromobenzene as the buffer gas accelerated bleaching as a result of the increased rate of intercombination transitions. Increasing the bromobenzene vapor concentration increased the triplet-triplet absorption of the active molecules, the quenching of the fluorescence being described by the Stem-Volmer equation. An estimate was made of the yield of triplet states in rarefield vapors. The rate constants for quenching of the singlet excited and triplet states of POPOP vapor were determined and found to be 8.6×10¹⁰ and 7.5×10⁸ liter·mole^–1·sec^–1, respectively.