Spectroscopic investigations and configuration-interaction-assisted crystal field analysis of Pr3+ in YPO4 single crystal

An optical study of a Y0.99Pr0.01PO4 single crystal is presented. Measurements of optical absorption, excitation, and emission by selective excitation into 1D2, 3P0 and 3P1, at different temperatures between 20 and 295 K, are described. A detailed account of the line assignments is given for absorption in the 4300–23 000 cm−1 spectral range, and for emission in the 6400–23 000 cm−1 range. The lifetimes of the emitting levels are determined. Vibronic sidebands accompanying absorption, emission and excitation spectra are reported. The decay processes of the 3P1, 3P0 and 1D2 levels are discussed. The aim of this study is a test of the configuration-interaction-assisted crystal field analysis as well as the accurate experimental determination of the energy level scheme. It was reported previously that the introduction of configuration interaction between the ground 4f2 configuration with the excited 4f6p configuration always resulted in a decrease (≈50–60%) in the standard deviations between the observed and calculated energy levels. In the present work the 4f5d configuration is included as well. The crystal field is analysed in the theoretical D2d site symmetry with and without configuration interaction. The results with 4f2, 4f2+4f5d, 4f2+4f6p and 4f2+4f5d+4f6p are given. The calculation on the basis of the 315 (4f2+4f5d+4f6p) levels gives the best overall standard deviation lowering it by 75% with regard to the calculation on the 91 4f2 levels only.