Optical spectra, energy levels and crystal-field analysis of Sm³⁺ in Na₃[Sm(oxydiacetate)₃] · 2NaClO₄ · 6H₂O

Abstract

Locations and assignments of 144 crystal-field energy levels are reported for Sm³⁺ in the trigonal Na₃[Sm(oxydiacetate)₃] · 2NaClO₄ · 6H₂O system. These energy levels span the 0–36 000 cm^-1 energy region, and they were located and assigned from optical emission spectra and from axial and orthoaxial (σ- and π-polarized) absorption measurements on single crystals. The principal SL parentages of the assigned levels span at least 20 Russell-Saunders terms within the 4f ⁵ electronic configuration of Sm³⁺, and these assigned levels represent nearly half the total number of crystal-field energy levels predicted to occur within the 0–36 000 cm^-1 region. The assigned levels are analysed in terms of a 26-parameter electronic hamiltonian in which six of the parameters are defined to represent the 4f-electron/crystal-field interactions for Sm³⁺ located at sites with trigonal dihedral (D ₃) symmetry. Of the 26 parameters, 22 (including the six crystal-field parameters) are used in fitting calculated energy levels to the experimental data, and excellent calculated-versus-experimental energy level fits are achieved. Fitted values obtained in this study for the Sm³⁺ ‘free-ion’ energy parameters are compared to those reported previously for Sm³⁺ in LaF₃ and LaCl₃. Quantitatively determined line strengths are reported for 50 (4f → 4f) crystal-field transitions observed in the single-crystal absorption spectra of Na₃[Sm(oxydiacetate)₃] · 2NaClO₄ · 6H₂O at 10 K.