STUDIES OF ION-PAIR INTERACTION IN KNDXGD1-XP4O12 CRYSTALS USING SITE SELECTION TIME RESOLVED SPECTROSCOPY

High resolution pulsed dye lasers were used to investigate the fluorescence of Nd**3** plus ions in KNd//xGd//1// minus //xP//4O//1//2 crystals. It was found that the low temperature excitation and absorption spectra exhibit the satellite structure. After selective excitation of the satellites the fluorescence spectra and lifetimes of the **4F//3/////2 state were recorded. These allowed to distinguish the single neodymium ions in perturbated crystal field sites as well as pairs of ions. Then, in the framework of the discrete host structure model using the measured quenching rates of the satellites the shape of the fluorescence decay was analyzed.