Spectrum of Nd3+ in Lanthanide Oxide Crystals

The ultraviolet, visible, and near‐infrared spectra of single‐crystal Nd₂O₃ and La₂O₃:Nd³⁺ observed at 10°, 80°, and 290°K, were analyzed. Over 300 absorption lines were assigned from the five crystalline Stark levels of the ground ${}^4{I}_{\frac{9}{2}}$ state to over 20 excited J manifolds in each crystal. In thick crystals, transitions to many excited levels from the higher Stark levels of the ${}^4{I}_{\frac{9}{2}}$ state were observed. The spectral assignments are compared with calculations of ``free‐ion'' energy levels and with the assignments of Y₂O₃:Nd³⁺. The parameters E¹, E², E³, and ξ are calculated for the three oxide crystals, and comparisons between observed and calculated energy levels are made. The significance of these parameters in comparison with those for Nd³⁺ in other crystals is discussed, and the effects of configuration interaction are pointed out.