Analysis and simulation of the optical spectra of the stoichiometric NdOF

Abstract

The UV–VIS–NIR absorption of the rhombohedral NdOF was measured at selected temperatures between 9 and 300 K. The emission spectra of NdOF, LaOF:Nd³⁺ and GdOF:Nd³⁺ were obtained at 4.2, 9, 77 and 300 K. The energy level scheme of the Nd³⁺ ion (the 4 configuration) derived from the optical spectra was simulated with a phenomenological model taking simultaneously into account both the free ion interactions and the crystal field (c.f.) effect for the C_3v point symmetry of the Nd³⁺ site in NdOF. The simulation yielded a good correlation (rms deviation 17 cm^-1) between the experimental and calculated energy level schemes of 122 Kramers doublets of a total of 182. The c.f. parameters show only slight distortion from the cubic O_h symmetry. The fourth and sixth rank c.f. effects have an important contribution to the overall c.f. interaction, while the contribution of second rank crystal field is small which indicates an important electrostatic interaction between the cation and anions. A comparison to Pr³⁺ (4), Sm³⁺ (4), Eu³⁺ (4), Tb³⁺ (4) and Dy³⁺ (4 electron configuration) in LnOF (Ln=lanthanide) shows a smooth evolution of the c.f. effect.