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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]

Optical absorption and emission measurements are reported for the Cs2NaDyCl6 and Cs2NaYCl6: Dy3+(5 mol %) systems under variable-temperature (10–298 K) conditions. For both systems, the data are compatible with the retention of octahedral (Oh) site symmetry at the Dy3+ ions over the entire 298 to 10 K temperature range. The only differentiation between the systems is the much greater quantum efficiency of 4F9/2 emission in the doped system vs that in the neat system. Forty-five crystal-field levels spanning 18 multiplets of the Dy3+ 4f9 electronic configuration are located and assigned, and an additional 12 crystal-field levels associated with six other multiplet manifolds are located, but left unassigned. These energy level results are analyzed on the basis of a nine-parameter 4f-electron Hamiltonian operating within a complete Russell–Saunders (SLJ) basis set for the 4f9 configuration of Dy3+. The most intense electric-dipole vibronic lines observed in the optical spectra are assigned to one-phonon vibronic transitions associated with the three odd-parity ‘‘moiety’’ modes of the DyCl3-6 octahedral clusters: ν3(t1u), ν4(t1u), and ν6(t2u). Intensity calculations are reported for both the no-phonon magnetic-dipole (origin) transitions and the one-phonon (ν3, ν4, and ν6) electric-dipole vibronic transitions. [ABSTRACT FROM AUTHOR]

Optical excitation and emission spectra are reported for the Cs2NaErCl6 system under variable-temperature (8.5–298 K) conditions. Detailed line assignments are made for the 4I15/2←4S3/2 and 4I15/2←4F9/2 high-resolution emission spectra, and all five crystal-field levels split out of the 4I15/2 ground multiplet are located. These results combined with our previously reported absorption results provide the locations of 35 crystal-field levels spanning 11 multiplets of the Er3+ ion in Cs2NaErCl6. Energy level calculations based on a nine-parameter 4f-electron Hamiltonian operating within the 4f11 configuration of Er3+ give results in good agreement with experiment. Excitation spectra for 4I15/2←4S3/2 emission are reported at several temperatures over the 340–540 nm spectral region. Emission spectra excited by near-ultraviolet radiation (centered at 383 nm) are reported over the 405–725 nm spectral region for sample temperatures ranging from 8.5 to 298 K. All but one of the seven multiplet-to-multiplet emission bands observed in this region decrease in intensity as the sample temperature is increased. The 4I13/2←4G11/2 emission exhibits an increase in intensity with increasing temperature. [ABSTRACT FROM AUTHOR]

Optical absorption and emission measurements are reported for the Cs2NaSmCl6 and Cs2NaYCl6:Sm3+ (1 or 30 mol %) systems under variable-temperature (10–298 K) conditions. Twenty-six crystal-field levels spanning 13 multiplets of the Sm3+ 4f 5 electronic configuration are located and assigned on the basis of the experimental data, and these energy level results are rationalized in terms of a nine-parameter 4f-electron Hamiltonian. The most intense electric-dipole vibronic lines observed in the spectra are assigned to one-phonon vibronic transitions associated with the three odd-parity ‘‘moiety’’ modes of the SmCl3-6 octahedral clusters ν3(t1u), ν4(t1u), and ν6(t2u). Intensity calculations are reported for both the no-phonon magnetic-dipole (origin) transitions and the one-phonon (ν3, ν4, and ν6) electric-dipole vibronic transitions. [ABSTRACT FROM AUTHOR]

Optical absorption and emission measurements are reported for the Cs2NaYCl6:Nd3+ (∼5 mol %) system under variable-temperature (4.2–296 K) conditions. The absorption measurements span the 12 000–24 000 cm-1 spectral region, and emission spectra are presented throughout the 13 300–18 860 cm-1 region. All the spectra are consistent with the retention of octahedral (Oh) site symmetry for the Nd3+ ions down to 4.2 K. Thirty-four crystal-field levels spanning 14 multiplets of the Nd3+ 4f3 electronic configuration are located and assigned on the basis of the experimental data. The most intense lines observed in each of the multiplet-to-multiplet transition regions are assigned to one-phonon (electric-dipole) vibronic transitions associated with the three odd-parity moiety modes of the NdCl3-6 cluster, ν3(tlu), ν4(tlu), and ν6(t2u). The ν3 lines generally appear as doublets (split by ∼10–15 cm-1) and are displaced from magnetic-dipole origins by ∼245–260 cm-1; the ν4 lines are displaced from origins by ∼100 cm-1, and are generally sharp and symmetric; and the ν6 lines are generally asymmetric in shape (or appear as doublets split by ∼2–6 cm-1), and are displaced from origins by 70–75 cm-1. Additional vibronic lines are observed persistently at displacement energies of ∼40–45 and ∼55–60 cm-1, but these lines are considerably less intense than those assigned to the ν3, ν4, and ν6 moiety-mode vibrations. The energy level data obtained from experiment is rationalized in terms of a 9-parameter model which includes the radial spin-orbit interaction parameter (ζso), the Slater–Condon one-particle electrostatic interaction parameters (F2, F4, and F6), the two-particle electrostatic configuration-interaction parameters (α, β, and γ), and the octahedral (Oh) crystal-field interaction parameters... [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]

Optical excitation and emission spectra are reported for the Cs2NaY0.3Tm0.7Cl6 and Cs2NaY0.99Tm0.01Cl6 systems. The spectra of these two systems are compared and their differences are rationalized in terms of concentration-dependent excited-state relaxation mechanisms. Energy level data derived from this study and from several previously reported studies on Cs2NaTmCl6 and Cs2NaYCl6:Tm3+ systems are summarized, and these data are analyzed in terms of a 16-parameter model Hamiltonian for the 4f 12 electronic configuration of Tm3+ in an octahedral (Oh) crystal field. Eight of the parameters in this Hamiltonian are used to ‘‘fit’’ the empirical energy level data. The parameter sets obtained from several data fits are presented and discussed. Magnetic dipole oscillator strengths are calculated for several sets of transitions, and the calculated results are compared to experimental observation. [ABSTRACT FROM AUTHOR]