What Factors Affect the⁵D₀Energy of Eu³⁺? An Investigation of Nephelauxetic Effects

Abstract

Relationships involving the interelectronic repulsion parameters, F(k) (k = 2, 4, 6), the spin-orbit coupling constant, ζf, and J-mixing, with the (5)D0-(7)F0 energy, E, have been investigated for Eu(3+) using various approaches. First, the linear relationship between E and the (7)F1 splitting (or the second rank crystal field parameter) is shown to be applicable not only to glasses but also to solid-state crystalline systems with Eu(3+) site symmetry of C2, C2v, or lower. In these cases, the change in (5)D0-(7)F0 energy is mainly due to the J-mixing effect of (7)F(J) (J = 2, 4, 6: most notably J = 2) which depresses (7)F0, whereas the (5)D0 energy is relatively constant. The (5)D0-(7)F0 energy also depends upon certain energy parameters in the Hamiltonian, in particular, F(k) and ζf. Model calculations show that increase in F(4) or F(6) produces an increase in E, whereas increase in F(2) produces a decrease in E. An increase in ζf produces a decrease in E. These findings are rationalized. Most previous 4f(6) crystal field calculations have only considered the F and D terms of Eu(3+) so that the Slater parameters are not well-determined. More reliable energy level data sets and crystal field calculations for Eu(3+) with fluoride, oxide, or chloride ligands have been selected, and certain of these have been repeated since most previous calculations have errors in matrix elements. The fitted Slater parameters have been corrected for the effects of three-body Coulomb interactions. Some systems do not follow the ligand trend F ~ O > Cl for Slater and spin-orbit parameters. From the limited data available, the average values of the corrected Slater parameters are greater for fluoride compared with chloride ligands, but the differences are comparable with the standard deviations of the parameters. There is no clear nephelauxetic series for these three types of ligands, with respect to spin-orbit coupling. Previous correlations of E with various parameters are of limited value because the (5)D0-(7)F0 energy difference not only depends upon the F(k) and ζf parameters but in addition is sensitive to the importance of J-mixing for low symmetry systems.

Parametrization of free ion levels of four isoelectronic 4f2 systems: Insights into configuration interaction parameters

“…We have introduced in Ref. [20] a concise, single measurement of inter-electronic repulsion, as the standard deviation (or second moment) of J-multiplet splitting, r ee . In terms of the Racah parameters E i , this quantity is defined:…”

“…where the coefficient in front of each Racah parameter is the square of the normalization constant required for the conversion of the Racah operator into unit operator (see [20] for details). This second moment is plotted against ionic charge (top abscissa scale) and (4Ài) 2 (lower scale) for the four free ions La + , Ce 2+ , Pr 3+ and Nd 4+ in Figure 2c.…”

“…Our current interest in nephelauxetic effects of lanthanide ions [1], representing changes in inter-electron repulsion from the free ion to that embedded in a crystalline host, necessitates the knowledge of free ion energy levels -which are surprisingly scant for 4f N electronic configurations. Presently we are investigating these inter-electronic repulsion effects for the 4f 2 ion Pr 3+ .…”

Structure and temperature effects on Nd3+ spectra in polycrystalline mixed scandium aluminum garnets Y3Sc Al5−O12

“…The 10 K data allow a comparative analysis of the electronic structure of Nd 3+ in YS x AG (x = 0, 1, 2) garnets in terms of the nephelauxetic effect, modification of free ion parameters [24] of the 2S+1 L J manifolds (that can be approximated by the experimental barycenters Bc) and of the crystal field that splits J manifolds. Table 1 shows that the differences between the barycenters of manifolds belonging to the same spectral term, such as Bc( 4 I 11/2 )-Bc( 4 I 9/2 ) are practically the same, regardless of composition x.…”

Synthesis, structure and red-emitting luminescence properties of Eu 3+ -activated perovskite-related tungstate Ba 4 Na 2 W 2 O 11

“…It has a simple electronic energy level scheme and its transitions are hypersensitive, i.e., they depend strongly on the chemical surroundings [1]. The luminescence spectra of Eu 3+ ions are characterized by some sharp peaks corresponding to electronic transitions from 5 D 0 to 7 F J (J=0- 6) states.…”