THE LUMINESCENT QUANTUM EFFICIENCY OF EU(2+) IONS IN ALKALI-HALIDES DETERMINED BY SIMULTANEOUS MULTIWAVELENGTH PHOTOACOUSTIC AND LUMINESCENCE EXPERIMENTS

In this work, the luminescent quantum efficiency of Eu2+ ions in alkali halides is determined by using a method based on the simultaneous and multiwavelength measurement of photoacoustic and luminescent signals after pulsed laser excitation. This method, which was first demonstrated in Eu2+-doped KCl, is now extended in order to include the possibility of direct non-radiative relaxation from upper excited states to the ground state. A high quantum efficiency is found for Eu2+ ions in different alkali halides (NaCl, KCl, KBr and KI).