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

Optical absorption and fluorescence spectra of the Kramers ions Ce3+, Sm3+, Dy3+, and Yb3+ in the C2 sites of Y2O3 are reported. A crystal-field analysis of these data and previously reported data for Nd3+ and Er3+ is performed that is based on a Hamiltonian of C2 point-group symmetry, including J-mixing effects. A best-fit analysis is performed for the ions Nd3+, Sm3+, Dy3+, and Er3+; resulting rms deviations between calculated and experimental levels range from 5.1 to 7.9 cm−1. Results of this analysis are used to obtain a smoothed set of crystal-field parameters for the entire lanthanide series; these smoothed parameters are used to predict the energy levels of Ce3+, Yb3+, and Gd3+ in Y2O3. Predictions for Ce3+ and Yb3+ are compared with experimental data.