Absolute quantum efficiency of an organic wavelength shifter using a pulsed ultraviolet source and temporal analysis

A novel technique for measuring an organic fluor quantum efficiency has been developed. The measurement involves evaluating the change in the luminescence temporal distribution as a function of solute concentration. The solute was excited by pulsed deep ultraviolet (UV) emissions and luminescence time spectra were measured by a time correlated signal photon counting technique. As the solute concentration is increased, the luminescence spectra have a decreased contribution from transmitted UV light and an increased contribution of solute fluorescence. The quantum efficiency of the solute is determined using these data along with a correction for the differences in the detection efficiency of the primary and secondary light. The correction was determined by an optical transport code, DETECT, and the measured photomultiplier tube spectral response. This paper demonstrates the technique with BaF₂ as the pulsed UV source resulting in the quantum efficiency of 9,10 diphenylanthracene in cyclohexane, weighted by the fast UV emissions of BaF₂, to be calculated as 0.76