Dimers and clusters in CaF2:Pr3+. Laser selective excitation and time-resolved spectroscopy

Publisher Website
Google Scholar
Abstract
Time-resolved and laser selective excitation experiments have been performed on CaF2:Pr3+ crystals at seven concentrations ranging between 0.05 and 2 mole Pr3+%. The time dependence of the energy transfer between two Pr3+ ions sitting at different sites is independent of concentration. Using polarised laser selective excitation at various temperatures between 1.4 and 4.2K, it is shown that these ions exist as dimers in the crystals even at very low concentration. The existence of higher-order clusters of Pr3+ ions is demonstrated through high-resolution analysis of the absorption spectra and correlated to the variations of the emission lifetimes of the various sites as a function of concentration. The interactions of the single ions and dimers with the clusters are discussed. These experiments show that the classical hypothesis of a random distribution of the dopant in ionic crystals must be handled very carefully.