Phonon and Electronic Raman Spectra of Cubic Rare-Earth Oxides and Isomorphous Yttrium Oxide*

Abstract

Laser-excited Raman spectra have been observed in single crystals of Y₂O₃, Y₂O₃(Eu³⁺), Er₂O₃, and YB₂O₃ at 10, 80, and 300 K. In Y₂O₃(Eu³⁺) the symmetries of the excited levels have been determined. The optically active phonons can be separated into two groups; in one group (above 300 cm⁻¹) the internal vibrations of (R.E.-O₆) octahedrons are preponderant, whereas in the other group (below 200 cm⁻¹) the translational motions of these octahedrons and the R.E. ions are dominant. In Y₂O₃(Eu³⁺) electronic transitions (²F₀ → ²F₂) of the Eu ions in C_3i-site symmetry have been observed and the symmetries of the crystal-field-split levels have been determined. Other effects, which may also be attributed to electronic Raman transitions, have been observed in Er₂O₃ and Yb₂O₃.