Luminescence properties of Pr3+ and Ce3+ in KCaF3 single crystals

The optical excitation and luminescence spectra of (Pr3+,Ce3+) ions in KCaF 3 are presented. High-resolution excitation and emission spectra of Pr3+ an d Ce3+ were measured at temperatures between 77 and 293 K. First measuremen ts of KCaF3 : Ce3+ crystal show that there are nonequivalent Ce3+ centers w hich radiate either in UV or visible range. The major Ce3+ nonequivalent ce nter in KCaF3 is Ce3+ ion in the site with tetragonal site symmetry (S-4). Energy levels for the 4f(2) ground configuration of Pr3+ in KCaF3 were esta blished from excitation and fluorescence spectra. Energy levels assignments were made assuming electric-dipole transition selection rules for S-4 site symmetry. Twenty-seven energy levels in the lowest six multiplets of the g round configuration were established. In the analysis of experimental data, the O-h magnetic-dipole selection rules were also considered to explain mi ssing or weak transitions which are allowed in S-4. Spectra of Pr3+ in KCaF 3 have been analyzed with a crystal-held Hamiltonians of S-4 or O-h symmetr ies including J mixing effects. Crystal-held parameters in these Hamiltonia ns have been determined by the minimization the RMS deviation between calcu lated and experimental energy Stark levels. We conclude that both model cal culations in the S-4 and O-h site symmetries for Pr3+ in KCaF3, provide the basis for a consistently good correlation with data. (C) 1999 Published by Elsevier Science B.V. All rights reserved.