The influence of the Tbetta level upon fluorescence and laser properties of aromatic compounds

Abstract

The fluorescence and laser properties of seven specially chosen aromatic compounds are studied at 293 ◦C. The quantum yield of fluorescence, γ, decay times, τf , of the deaerated and non-deaerated solutions are measured. The oscillator strength, fe, fluorescence rate constants, kf , natural lifetimes, τT 0 , and intersystem crossing rate constants, kST, are calculated. Some laser parameters are calculated or measured experimentally. It is found that the position of the T level plays an important role in the fluorescence and laser properties of aromatic compounds. If the T level is situated below the Sp level, it decreases the quantum yield of fluorescence and the decay time and increases the threshold of laser action. If, due to some structural changes of a molecule, the T level is situated higher than the Sp level, then the quantum yield of fluorescence and the decay times are increasing and the threshold of laser action is decreasing. Such influence of the position of the T level upon fluorescence and laser properties of aromatic compound is explained by the fact that the Sp level mixes with the T level more readily than with other τ ∗ levels.