Determination of two-electron crystal field parameters in some neodymium compounds

M. Faucher; O. K. Moune; D. Garcia

doi:doi:10.1051/jp2:1993176

Numéro		J. Phys. II France Volume 3, Numéro 7, July 1993


Page(s)		961 - 969
DOI		https://doi.org/10.1051/jp2:1993176

DOI: 10.1051/jp2:1993176
J. Phys. II France 3 (1993) 961-969

Determination of two-electron crystal field parameters in some neodymium compounds

M. Faucher¹, O. K. Moune¹ and D. Garcia²

¹ ERS 70 du CNRS, PCM, Ecole Centrale, Grande Voie des Vignes, 92295 Chatenay-Malabry Cedex, France
² SII, 83 Bd Vincent Auriol, 75013 Paris, France

(Received 14 January 1993, revised 15 March 1993, accepted 9 April 1993)

Abstract
Two-electron, fourth rank ( k=4), crystal field parameters are fitted for four neodymium compounds : LiYF ₄ : Nd ³⁺, Nd ₂O ₂S, Y ₂O ₃ : Nd ³⁺ and Nd ₂O ₃, displaying a strong experimental/calculated discrepancy for the ²H _11/2 level. The final mean deviation for all the levels is 2 cm ^-1 (20 %) lower than that attained with the standard (one-particle) theory. The compound parameters $b_{q}^{\{k_{1}k_{2}\}\;k}$ involve odd and even combinations of k₁ and k₂. The geometrical dependence (q) seems to indicate a drift towards a C $_{\infty{\rm v}}$ site symmetry caused by axial ligands. The diagonal matrix elements of the correlated crystal field are smaller than the off-diagonal matrix elements except for twin terms.