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.

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.

The absorption and fluorescence spectra of Eu3+ in single crystals of Y2O3 have been observed and analyzed. The intermediate-coupling free-ion energy levels for Eu3+, including the effects of the 46 singlet states of the 4f6 configuration, are presented for all levels appearing below 41 000 cm—1. The results obtained by including the singlet states in the free-ion energy level calculations are discussed. Values of E1=6217.84 cm—1, E2=38.94 cm—1, E3=630.15 cm—1, and ζ=1343.1 cm—1 are found to give the best over-all agreement between the observed and calculated energy levels.

A spectroscopic Judd–Ofelt investigation has been performed on Er3+ in the doubly doped phosphate glass:Er3+, Yb3+ in order to assess its potential as a laser system. The standard Judd–Ofelt model was applied to the room-temperature absorption intensities of Er3+(4f11) transitions to determine the intensity parameters: Ω2=6.28×10−20 cm2, Ω4=1.03×10−20 cm2, and Ω6=1.39×10−20 cm2 in the phosphate glass host. The intensity parameters are used to determine the radiative decay rates (emission probabilities of transitions) and branching ratios of the Er3+ transitions from the excited-state J manifolds to the lower-lying J′ manifolds. The radiative lifetimes of these excited states are determined from the radiative decay rates. The predicted decay rates and radiative lifetimes are compared to those of Er3+ transitions in other glass hosts. The quantum efficiency of the eye-safe laser transition I13/24→4I15/2 (1.54 μm) of Er3+ is approximately 80% in the phosphate glass host.

We report an analysis of new and previously existing optical absorption and fluorescence data, far-infrared data, and electronic Raman scattering data for Eu3+, Dy3+, and Er3+ in the C3i sites of Y2O3 and R2O3, where R=a rare earth. Our previous analysis of C2-site spectra yields an effective point-charge model for the host lattice that allows initial estimates to be calculated for the C3i-site crystal-field parameters Bkm. Best-fit values of B20, B40, and B43 are obtained for Eu, and best-fit values of all Bkm allowed by symmetry are obtained for Dy and Er. The best-fit Bkm are in relatively poor agreement with the model; in particular, B20 has the opposite sign from and B44 is much smaller than the model predictions. From the best-fit Bkm we obtain phenomenological crystal-field components Akm, from which we predict Bkm and C3i -site energy levels for the ground states of Tb3+, Ho3+, Tm3+, and Yb3+. While the effective point-charge model is apparently too crude to make accurate, quantitative, a priori predictions, the model and the data allow one to predict confidently the behavior of ions doped into C3i sites for which no data exist.