The influence of the Tβ 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, τ f, of the deaerated and non-deaerated solutions are measured. The oscillator strength, f e, fluorescence rate constants, k f, natural lifetimes, τ 0 T, and intersystem crossing rate constants, k ST, are calculated. Some laser parameters are calculated or measured experimentally. It is found that the position of the T β level plays an important role in the fluorescence and laser properties of aromatic compounds. If the T β level is situated below the S p 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 β level is situated higher than the S p 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 β level upon fluorescence and laser properties of aromatic compound is explained by the fact that the S p level mixes with the T β level more readily than with other τ ππ* levels.