Optical spectra, energy levels, and crystal-field analysis of tripositive rare-earth ions in Y2O3. II. Non-Kramers ions in C2 sites

Abstract

Optical absorption and fluorescence spectra of the non-Kramers ions Pr3+, Tb3+, and Ho3+ in the C2 sites of Y2O3 are reported. A crystal-field analysis of these data and previously reported data for Eu3+ and Tm3+ is performed that is based on a Hamiltonian of C2 point-group symmetry, including J-mixing effects. A best-fit analysis is performed for all five ions; resulting rms deviations between calculated and experimental levels range from 2.8 to 26.4 cm−1. Results of this analysis and of our previous analysis of Kramers ions in C2 sites are used to obtain a set of phenomenological crystal-field components Akm for the C2 sites. We predict the crystal-field splittings for Pm3+ in Y2O3, and we compare our previous prediction of the splittings of Gd3+ in Y2O3 with recently reported measurements. We also describe an effective point-charge model for the Y2O3 lattice in which good agreement between calculated and phenomenological Akm is obtained with qY1 = 2.53, qY2 = 1.26, and q0 = −1.052. (The quantities qY1, qY2, and q0, are, respectively, the charges on the C3i yttrium site, the C2 yttrium site, and the oxygen site, in units of e.) With this model, we calculate Akm for the C3i sites.