ENERGY-LEVELS OF CR3+ IONS IN C3I SITES OF Y3AL5O12

From an analysis of the ultraviolet absorption spectrum of Cr3+ ions in Y3Al5O12 we have obtained a sufficient number of energy levels to perform a crystal-field splitting calculation for Cr3+ ions in sites of C3i symmetry in the lattice. The Hamiltonian used included Coulombic, crystal-field (C3i symmetry), spin-orbit interaction, and effective interconfiguration interaction terms and was diagonalized within the complete basis for 3d3 atomic configuration. The calculated energy levels were compared with experimental levels up to 40000 cm-1. From the data, we have assigned 29 Stark levels to Cr3+ ions in C3i sites which agree with calculated levels to within an rms deviation of 18 cm-1. The values of the parameters that give the best agreement are F(2) = 52724, F(4) = 38380, zeta = 252, alpha = 132, gamma = -124, B20 = 1091, B40 = -21574, and B43 = 27224 cm-1 (Dq = 1605, nu = 891, and nu' = -104.8 cm-1). The crystal-field splitting of Cr3+ levels in S4 lattice sites is also predicted with the use of the free-ion parameters obtained in this paper and a point-charge lattice-sum model.