Lanthanides-relative intensity

When Wjcr A+, this probability is small, and the relative intensity of the well screened peak is small when Wjcr A+, the contrary occurs. The d-transition and lanthanide metal pictures represented in Fig. 7 are therefore generated. 

In solutions, the energy of the 4f—> 5d transitions is lowered by about 15000 cm-1 as compared to gaseous ions and the corresponding parity allowed and relatively intense bands are observed in the ultraviolet region in Ce3+, Pr3+ and Tb3+ ions. As shown in Fig. 8.14, the electronic absorption spectra of the majority of the trivalent lanthanides in the UV-vis spectral range involves only f-f transitions. 

The shapes and intensities of spectral bands were used in complexation studies of lanthanide nitrates in organic solvents. The degree of complexation of nitrate was in the order water > methanol > acetonitrile. The tendency of the nitrate anion and the solvent molecules to compete for coordination followed the order DMF > TBP > NOJ > H2O > C2H5OH > dioxane. The 4f-4f spectral band of Nd(C104>3 in DMF, DMSO and DMSO-H2O mixtures split into two components whose relative intensities were attributed to different amounts of nona- and octacoordinated Nd(III) solvated ion. The major species are [Nd(DMF)9]3+/[Nd(DMSO)9]3+ and the minor species are [Nd(DMF)8]3+/[Nd(DMSO>9]3+. Addition of water to the equilibrium mixture resulted in a shift of the equilibrium to predominantly nonacoordinated species due to substitution of DMF/DMSO by water along with a red shift of the spectral band [224,225]. 

Anodier stone that has found wide cultural use as a carving medium in many early societies is steatite or soapstone, a very soft metamorphic rock related to chlorite and talc. In this laboratory, steatite (actually chlorite) from quarries near Tepe Yahya (Iran) was characterized by observation of the ratios of the relative intensities of basal-plane x-ray diffraction peaks after it was found that NAA-determined trace element concentrations varied wildly within a given specimen. Another technique that has been used involves the determination by NAA of a number of lanthanide elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Ho, Er, Tm, Yb and Lu) and the taxonomy of their abundances relative to each other — in other words, true pattern recognition , when plotted as ratios to the levels of the same elements in a standard reference chondrite Although this technique found successful provenience application... 

Such terms are equivalent to those obtained by Satten et al. (1983) in their study of the excitations of the T,u vibrational mode of the octahedral complex UCI5 at 260 cm L They were aware that their approach would work in a similar way for lanthanide complexes their choice of an actinide was partly determined by their familiarity with the UClj complex. Another important consideration was the high symmetry of the uranium site, which greatly reduces the number of intensity parameters required in the analysis. To assess the situation we note first that the possible pairs (k,t) in expression (94) are (1,2), (3,2), (3,4), (5,4), (5,6) and (7,6). The number of Ti representations of 0(, that occur in the representations of 0(3) are 1, 1,2 and 2 for /c = 1, 3, 5 and 7, so we expect 9 parameters in all. Satten et al. (1983) reduced that number to 6 by carrying out a complete closure over all virtual electronic states, which has the effect of fixing the ratio of the two operators (94) for which t = /c 1. They were able to account quite well for the relative intensities of some 20 or so transitions of the type Aig( H4)-> T, ( Lj), where is a... 

CeRu3B2- The two 4f-derived peaks in CeRhjBj were at the same energy as in the measurements of Sampathkumaran et al. but the relative intensities differed, probably because Maple et al. corrected for inelastically scattered electrons while Sampathkumaran et al. did not. CeRujBj also showed two 4f-derived peaks which were located nearer the Fermi energy than in the Rh-based compound and had relative intensities indicative of more Ce-Ru 4f—4d hybridization than Ce-Rh 4f—4d hybridization. Maple et al. argued that as the strength of the Ce 4f-derived peak near the Fermi level increased, magnetism would be suppressed, in contrast with Sampathkumaran et al. Unfortunately, Sampathkumaran et al. varied the hybridization by changing the lanthanide, while Maple et al. varied the transition metal. 

This example with Eu and Pd demonstrates first of all how the valence state of a lanthanide can be determined by the presence of the well separated Ln and Ln emission features. For the mixed-valent compound it is furthermore possible to establish the degree of valence mixture from the relative intensities of the two emission features. The relative stabilities of the divalent and trivalent configurations are also revealed by the position of the divalent photoemission features in the different compounds. Therefore one can determine for each compound by how much the divalent configuration is stabilized by the surface. 

Fig. 11. The 4d->4f core electron energy loss spectra of the lanthanides. Spectra are shown for two primary energies E. The theoretical relative intensities of electric dipole transitions of Sugar (1972a) are shown where available (Strasser et al. 1985a).

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