PHOTOACOUSTIC DETERMINATION OF THE LUMINESCENT QUANTUM EFFICIENCIES OF F-2+ AND (F-2+)H CENTERS IN NACL-OH- CRYSTALS

Photoacoustic (PA) measurements of F2+ centres in additively coloured NaCl:OH- crystals have been carried out. The 1.06 mu m line of a pulsed Nd:YAG laser was used for excitation and the PA signal was detected with a piezoelectric detector. The F2+ centres were produced by photoaggregating samples in situ, allowing measurements of the PA signal as a function of the centre concentration to be obtained without altering the experimental geometry. In agreement with previous observations of temperature independence for both lifetime and luminescence intensity, a quantum efficiency of almost 100% was measured. The relative quantum efficiency of (F2+)H centres was determined by a comparison of the luminescent emissions of both centres at liquid-nitrogen temperature.