Laws governing laser radiation from 2-hetaryloxazoles and their cations

An investigation was made of laser radiation from 2-hetaryloxazoles and their cations. It was found that for these compounds there was typically no agreement between the lasing characteristics in series of similar compounds and there was no correlation between the threshold pump energy and the fluorescence quantum efficiency of the dye. For this class of compounds, an anomalous relationship was observed between the wavelengths of the lasing and fluorescence maxima, and the lasing threshold in the neutral forms was also considerably higher than that of the cationic forms. These features can be attributed to a high-intensity S₁→ S_n absorption band near the fluorescence maximum of the neutral forms of the dye.