Optical Studies of Energy Levels in Eu(OH)3

The energy levels of Eu(OH)₃ have been determined from the absorption and fluorescence spectra at 4.2 and 77°K. A crystal field analysis of the ⁷F manifolds, including intermediate coupling and the J‐mixing effects of the crystal field, gave best agreement for $B_{20}\text{= 211\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}{\mathrm{,\hspace{0.17em}B}}_{40}\text{= −72\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}{\mathrm{,\hspace{0.17em}B}}_{60}\text{= −52\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}$ , and $B_{66}\text{= 611\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}$ . The above parameters also gave a good fit to the ⁵ D manifolds. Using these crystal field calculations and the free ion level structure of Carnall, Fields, and Rajnak, it was possible to identify nine levels in the ⁵L₈ and ⁵L₉ levels, which were found directly below and above the ⁵D₄ manifold and are strongly mixed with it. The over‐all rms deviation for the levels in the ⁷F, ⁵D, and ⁵L manifolds was 4.9 cm⁻¹. The above crystal field parameters have been compared with previous results for other rare earth hydroxides: Gd(OH)₃, Tb(OH)₃, Dy(OH)₃, Er(OH)₃, Gd³⁺:Y(OH)₃, Tb³⁺:Y(OH)₃, Ho³⁺:Y(OH)₃, and Er³⁺:Y(OH)₃. Phonons in the rare earth hydroxides are discussed briefly, with results presented from the vibronic transitions in Eu(OH)₃ and the phonon Raman effect in Tb(OH)₃.