Correlation-crystal-field analysis of the2H(2)11/2multiplet ofNd3+

Orthogonal correlation-crystal-field (CCF) operators for the ${\mathit{f}}^{\mathit{N}}$ configuration have been discussed in an earlier paper, with emphasis on the anomalous multiplets ${}_{}{}^3{}_{}{}^{}$ ${\mathit{K}}_8$ of ${\mathrm{Ho}}^{3+}$ and ${}_{}{}^6{}_{}{}^{}$ ${\mathit{I}}_{17/2}$ of ${\mathrm{Gd}}^{3+}$. In those cases the ${\mathbf{g}}_3^{\mathrm{}\left(6\right)\mathrm{}}$ operator, which is a major component of the sixth-rank spin-correlated crystal-field operator, was found to be useful. In this paper we turn our attention to the ${}_{}{}^2{}_{}{}^{}$H(2${)}_{11/2}$ multiplet of ${\mathrm{Nd}}^{3+}$. The one-electron crystal-field parametrization consistently underestimates the splitting of this multiplet, and several possible corrections have recently been suggested in the literature. We show, by analyzing the spectrum of ${\mathrm{Nd}}^{3+}$ in several host crystals, that the addition of the fourth-rank orthogonal CCF operator ${\mathbf{g}}_{10\mathit{A}}^{\mathrm{}\left(4\right)\mathrm{}}$ to the Hamiltonian removes the anomaly. Our fits are in qualitative agreement with ab initio calculations of CCF effects for lanthanide ions.