Symmetry, selection rules, and energy levels of Pr 3+:Y 3Al 5O 12

Abstract

Absorption, fluorescence, and site-selective excitation spectra of Pr 3+: Y 3Al 5O 12 are reported between 0.4 and 6.7 μm at several temperatures between 1.6 and 90 K. The complexity of the spectra indicates that Pr 3+ ions occupy several different sites. The most intense spectra, representing the majority of the Pr 3+ ions in dodecahedral lattice sites, are analyzed on the basis of electric-dipole selection rules for D 2 site symmetry. Weak spectra are reported but not analyzed due to the difficulty in assigning levels to a particular site. Analyses of intense spectra establish the symmetry of 17 Γ 1, 12 Γ 2, 10 Γ 3, and 12 Γ 4 Stark levels. These 51 levels are compared with the results of a crystal-field splitting calculation. A Hamiltonian consisting of Coulombic, spin-orbit, and crystal-field (D 2 symmetry) terms was diagonalized for all manifolds of the Pr 3+ (4f 2) configuration. The rms deviation between calculated and experimental levels is 11 cm −1.