Lanthanide ions energy levels

Location of Lanthanide Ion Energy Levels Relative to Those of the Host... 

The field of lathanide lasers is mature but not exhausted. Additional laser schemes and materials will undoubtedly be exploited. There are 1639 free-ion energy levels associated with the 4fn electronic configurations of the thirteen trivalent lanthanides. Yet, of the 192,177 possible transitions between pairs of levels, by mid-1979 only 41 had been used for lasers. It is certain that given suitable pump sources and materials, stimulated emission involving many... 

This basic parameterization scheme, used at the time of the last A.C.S. symposium on lanthanide and actinide chemistry ( 5), has been discussed in detail by Wybourne 06). In applying the scheme, the free-ion Hamiltonian was first diagonalized and then the crystal-field interaction was treated as a perturbation. This procedure yielded free-ion energy levels that frequently deviated by several hundred cm from the observed energy levels.a In addition, the derived parameters such as the Slater radial integral, f(2), and the spin-orbit radial integral did not follow an expected systematic pattern across the lanthanide or actinide series ( 7). ... 

The free-ion energy levels up to approximately 30000 cm for all of the tripositive lanthanide ions in LaCl3 single crystals are shown in Figure 1. Crosswhite (16) has recently tabulated and discussed the free-ion and crystal-field parameters needed to describe the lanthanide data. The tripositive actinide levels are shown in Figure 2. Table I summarizes the free-ion parameters for the actinides which have been studied in detail. The detailed analyses of the U3+ and Np3+ ions have recently been completed (17, 18). The analyses presented in Table I for Pu3+, Am3+, and Cm3+ are based on published spectra (19, 20, 21, 22) obtained by Conway and coworkers. 

The wave functions used in the expressions for the line strengths are precisely those deduced by an analysis of the free-ion energy level structure. Therefore, only three new parameters, the s, have been introduced to account for the line strengths. This scheme has been remarkably successful in modeling experimental observations in both crystal and solution environments. It also accommodates the existence of the "hypersensitive" transitions. Peacock (30) has recently reviewed the field with regard to lanthanide f-f transitions. The simplicity of this scheme has been utilized by Krupke (31) and Caird (32) to predict potential laser transitions in the lanthanides. 

Comparison of energy-level model parameters (in cra ) used in calculating 3+ lanthanide and actinide free-ion energy levels for f through f configurations. Lanthanide parameters are from Carnall et al. (1989) and actinide parameters are from Carnall (1992), n denotes the number of 4f or 5f electrons. 

The spectroscopic properties of lanthanide ions have already been the subject of several chapters in this series, The atomic lanthanide spectra and the theoretical methods for free-ion energy level calculation were reviewed by Goldschmidt (1978). Fulde (1979) considered the crystal fields in rare-earth metallic compounds. Attention was given to the determination of crystal-field parameters in opaque materials, for which no optical methods can be used. In a chapter concerning the complexes of the rare earths, Thompson (1979) paid attention to the spectroscopic properties of coordination compounds. Camall (1979) discussed the absorption and fluorescence spectra of rare-earth ions in solution. Weber s contribution (1979) treated rare-earth lasers and that of Blasse (1979) treated phosphors activated by lanthanide ions. Morrison and Leavitt (1982)... 

In what follows we briefly review some of the previous attempts to analyze the available spectra of plutonium (6). In addition, we estimate energy level parameters that identify at least the gross features characteristic of the spectra of plutonium in various valence states in the lower energy range where in most cases, several isolated absorption bands can be discerned. The method used was based on our interpretation of trivalent actinide and lanthanide spectra, and the generalized model referred to earlier in the discussion of free-ion spectra. 

Figure 3 Energy level diagram for selected luminescent lanthanide ions.

The lanthanides have electrons in partly filled 4/orbitals. Many lanthanides show colors due to electron transitions involving the 4/orbitals. However, there is a considerable difference between the lanthanides and the 3d transition-metal ions. The 4/ electrons in the lanthanides are well shielded beneath an outer electron configuration, (5.v2 5p6 6s2) and are little influenced by the crystal surroundings. Hence the important optical and magnetic properties attributed to the 4/ electrons on any particular lanthanide ion are rather unvarying and do not depend significantly upon the host structure. Moreover, the energy levels are sharper than those of transition-metal ions and the spectra resemble those of free ions. 

The colors are characteristic of the ions themselves and are due to transitions between the partly filled d orbitals of transition metals (d-d transitions) or the partly filled / orbitals of lanthanides (f-f transitions). In the 3d transition-metal ions, the 3d orbitals contain one or more electrons. When these ions are introduced into a solid, the orbital energies are split by interactions with the surrounding anions. The color observed is due to transitions between these split energy levels. The color observed varies considerably as the interactions are dependent upon the... 

Fig. 8 Energy level diagrams for the dansyl units of dendrimer 11 and the investigated lanthanide ions. The position of the triplet excited state of 11 is uncertain because no phosphorescence can he observed...

Figure 6.1 An energy-level diagram for trivalent lanthanide rare earth ions in lanthanum chloride (after Dieke, 1968).

All lanthanide ions, with the exception of gadolinium(III) and europium(II), are likely to be relaxed by Orbach-type processes at room temperature. In fact, the f" configurations n l) of lanthanides(III) give rise to several free-ion terms that upon strong spin-orbit coupling, provide several closely spaced energy levels. Table III reports the multiplicity of the ground levels, which varies from 6 to 17, and is further split by crystal field effects. 

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