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Free-ion and crystal-field energy parameters for trivalent lanthanide ions (Ln3+) in Cs2NaLnCl6 and Cs2NaYCl6 are presented and discussed. Spin-correlated crystal-field parameters are determined for those systems for which sufficient data are available. The superposition model is used to compare the crystal-field interactions in the Cs2NaYCl6:Ln3+ and LaCl3:Ln3+ systems. [ABSTRACT FROM AUTHOR]

The best available energy level data for the cubic Cs2NaLnCl6 and Cs2NaYCl6:Ln3+ (doped) systems are collected together and summarized. These data are analyzed in terms of a parametric model which assumes an octahedral (Oh) site symmetry for the Ln3+ ions and a 4 f N ‘‘free-ion’’ Hamiltonian similar to that used previously in energy level analyses of the LaCl3:Ln3+ systems. The empirical energy level data are fit to the parametrized 4 f N Hamiltonian, and the resulting ‘‘best-fit’’ parameter sets and calculated energy levels are presented and discussed. [ABSTRACT FROM AUTHOR]

The magnetic-dipole moments associated with 4f → 4f radiative transitions in lanthanide complexes are usually calculated on the basis of a static crystal-field model in which the ligands’ influence is confined to mixing (and splitting) the 4fN eigenstates of the ‘‘free’’ lanthanide ion. In this model the ligand charge distributions are assumed to be passive to the radiation field, with the latter acting only on the ligand-perturbed 4fN states of the lanthanide ion. Here we consider another model in which the ligand charge distributions are assumed to be polarized by the radiation field and then coupled to 4f → 4f electric-multipolar transition moments to effect a resonant magnetic-dipole interaction with the radiation field. This model (or mechanism) is exactly analogous to the dynamic-coupling (or ligand-polarization) model described previously for lanthanide 4f → 4f electric-dipole transition moments [see, for example, J. Phys. Chem. 88, 3579 (1984)]. It is shown that the dynamic-coupling (DC) mechanism for 4f → 4f magnetic-dipole transition moments will be competitive with the static-coupling (SC) mechanism only for transitions with strong |ΔJ|>1 character, and even for these transitions the DC contributions to total magnetic-dipole strength are predicted to be small (<10-7 D2). However, it is also shown that the DC contributions to the electric- and magnetic-dipole transition moments of 4f → 4f transitions in chiral lanthanide systems may be crucial to explaining (or rationalizing) the rotatory strengths of these transitions. The latter suggestion is especially applicable to transitions whose intensities are known to be hypersensitive to the ligand environment. [ABSTRACT FROM AUTHOR]