Normal lanthanides

Whereas there are experimental evidences for the band behaviour of 5 f electrons up to plutonium (Z = 94) (see Table 3), the same criteria show that suddenly americium (Z = 95) behaves like a normal lanthanide having well localized 5f electrons ( and Chap. C) ... 

The following statistical analysis in which standard statistical methods (3) have been modified to our special problem of fitting regression lines to normalized lanthanide patterns has been performed by Kolboe (9). 

Results of the weighted regression analyses of the data for the eleven distributions are summarized in Table V. The normalized lanthanide patterns for the two samples which have the smallest (B.14) and largest... 

In addition to Dy2Fe2Si2C, R2Fc2Si2C (R = Pr, Nd, Y, Gd, Tb, Ho, Er) were also prepared and were recognized to be isotypic by examination of X-ray photographs of powdered samples. The variation of the cell parameters is a consequence of the normal lanthanide contraction. 

This section is divided into two parts. In sect. 4.2 experiments on normal lanthanides, i.e. those in which the 4f" configuration is believed to be stable, are reviewed. Except in the case of neodymium and thulium, the transitions so far observed are J J l. This is because the J J 2 transitions, which are not... 

All lanthanide compound series exhibit the lanthanide contraction when one considers the molar volume of the compound. But in four of the compound series which have the tetragonal ThCr2Si2-type structure the c lattice parameter actually expands, but a decreases sufficiently such that the unit-cell volume shows the normal lanthanide contraction (Gschneidner 1986). These compound series are RM2Si2, with M = Cu, Ag and Au, and RCu2Ge2- Although this lanthanide expansion was originally observed over 15 years ago, no one has proposed an explanation. 

Fig. 32. PAAS-normalized lanthanide patterns for early Proterozoic uranium deposits from the Pine Creek Geosyneline, Australia (data are from McLennan and Taylor 1979). Compared to the unmineralized host sedimentary roek, these deposits are extremely enriched in heavy lanthanides and depleted in light lanthanides. The abundances and amount of fractionation is related to the U content, suggesting the lanthanide mobility and U mineralization are directly related, thus helping to constrain the origin of the deposit. The fractionation of Sm and Nd during ore-formation allows dating by the Sm-Nd method.

The focus of interest in homogeneously mixed valence is the 4f electron de-localization. In normal lanthanide solids (which have by definition integral lanthanide valence), the number of inner 4f electrons is integral. Moreover the 4f electrons then remain completely localized on a given lanthanide atom as all other inner core electrons there is no 4f band formation. The outer 5d6s valence electrons are delocalized conduction electrons (Wannier states of the solid). 

Normal lanthanide and actinide behavior versus heavy-electron behavior... 

Lanthanide distribution models (Elderfield 1988, Byrne and Kim 1993, Erel and Morgan 1991, Erel and Stolper 1993) provide a basis for the comparative shale-normalized lanthanide concentrations (lanthanide fractionations) which are observed in the oceans. Lanthanide fractionation models are formulated in terms of competitive complexation equilibria involving, on one hand, solution complexation, and on the other, surface complexation on marine particles. Following the developments of Elderfield (1988) and Byrne and Kim (1993), shale-normalized lanthanide concentrations (Mj)sn in seawater can be expressed as... 

Fig. 8. Shale-normalized lanthanide compositions of 0.22 (tm filtrates of the Amazon, Fly (Papua New Guinea) and Mississippi River waters. Amazon and Mississippi data from Sholkovitz (1993, 1995) Fly River data from unpublished work of Sholkovitz. G/J Avg. refers to the averaged river water composition of Goldstein and Jacobsen (1988a).

Fig. 38. Shale-normalized lanthanide patterns for CHEER 6 (26 July 1988) filtered samples comparison of oxic Surface waters, anoxic bottom waters, and anoxic upper porewater. Also shown is the pattern resulting from the normalization of the lanthanide concentrations of the anoxic bottom waters relative to the lanthanide concentrations of the oxic surface waters. From Sholkovitz et al. (1992).

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