Fluorescence quenching of Nd3+ in LaF3 studied by direct measurements on pairs

The self-quenching of the Nd3+ infrared fluorescence in LaF 3 has been studied by the direct measurement of the transfer rates for various classes of Nd3+ pairs. Using weakly doped samples, the pairs are isolated and their behaviour is intrinsic. The results obtained at 1.2 K are used to predict the properties of concentrated crystals. From the difference between the predicted behaviour and the experimental results reported by others, it is concluded that migration of the excitation among the donors plays a prominent part. This situation, unusual at low temperatures, is discussed. Other results as existence of a short range interaction, transfer rates inside (Pr, Nd) pairs, efficiency of three ions processes are also discussed.