Determination of the absolute quantum efficiency of the luminescence of crystalline anthracene and of meso–dimeso derivatives using photoacoustic spectroscopy

Abstract

In this study, photoacoustic spectroscopy (p.a.s.) has been employed as a calorimetric method for the determination of the luminescent quantum efficiency (η_F) of several solid materials: 1,4-bis(4-methyl-5-phenyloxazol-2-yl)benzene, anthracene and eleven meso and dimeso anthracene derivatives. The technique used utilizes the phenomenon of photoacoustic saturation, in which the amplitude of the p.a. signal is independent of the absorption coefficient of the samples. Fluorescence quantum efficiency values of some anthracenes have also been determined using fluorescence measurements relative to pyrene crystals and they are shown to give results consistent with p.a. values. These data have been interpreted to estimate the relative rates of photodimerization of meso anthracenes in their crystal forms, and evidence for the existence of the 9-phenylanthracene crystal dimer is found in the p.a. spectra.