Number Of Lanthanide Research Articles

Resonant Raman scattering in Nd 2O 3 and the electronic structure of Sr 2RuO 4 studied by synchrotron radiation excitation

This paper is intended to illustrate two points. The first is the extensive growth of resonant Raman soft X-ray scattering due to the emergence of third-generation X-ray sources. With these sources, the ubiquitous presence of Raman scattering near the 3d and 4d ionization thresholds has been used to elucidate the excitation process in a number of rare earth and transition metal compounds. Such scattering can produce dramatic changes in the emission spectrum, as we show in our example of inelastic scattering at the 3d threshold of Nd 2O 3. Photon-in photon-out soft X-ray spectroscopy is adding a new dimension to soft X-ray spectroscopy by providing many opportunities for exciting research, especially at third-generation synchrotron light sources. Second, it is very effective to use theory and experiment to characterize the electronic properties of materials. In particular we confirmed in-plane oxygen–ruthenium bonding in Sr 2RuO 4, the first copperless perovskite superconductor, by analyses using calculations, soft X-ray emission spectroscopy (SXE) and photoelectron spectroscopy (PES). Measurements of this type illustrate the importance of combining SXE and PES measurements with theoretical calculations.

Examples of soft X-ray emission and inelastic scattering excited by synchrotron radiation

This paper is a summary of some of the recent activities of our soft X-ray spectroscopy collaboration. We are using soft X-ray emission spectroscopy to probe the electronic properties of matter, emphasizing atoms in the bulk and at interfaces. In particular we have used incoherent photon excitation to obtain a basic understanding of the electronic properties of a wide variety of materials including Sr 2RuO 4, a new superconductor. In this first copperless perovskite superconductor, we confirmed in-plane oxygen–ruthenium bonding by analysis using calculations and soft X-ray emission spectroscopy and photoelectron spectroscopy. In the case of the sulfides, the sulfur in FeCuS occupies a single site, and the sulfur in CuS forms dimers at two thirds of the sites. This behavior was confirmed by calculation and by measurement of soft X-ray emission spectra excited at different photon energies near the sulfur L 2,3 absorption edge, and by core photoemission measurements. Measurements of this type illustrate the importance of combining SXE and PES measurements with theoretical calculations. The ubiquitous presence of Raman scattering near the 3d and 4d ionization thresholds has been used to elucidate the excitation process in a number of rare earth and transition metal compounds. Such scattering can produce dramatic changes in the emission spectrum that can further the basic understanding of the atomic excitation process in these compounds. Photon-in photon-out soft X-ray spectroscopy is adding a new dimension to soft X-ray spectroscopy by providing many opportunities for exciting research, especially at third generation synchrotron light sources.

Synthesis, crystal structures and NMR and luminescence spectra of lanthanide complexes of 1,4,7,10-tetraazacyclododecane with N-methylene(phenyl)phosphinic acid pendant arms †

Complexes of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayltetramethylenetetrakis(phenylphosphinic acid) H4L1 with yttrium and a number of lanthanides were synthesized and the crystal structures of Li[LaL1(H2O)]·10H2O and Li[CeL1(H2O)]·10H2O determined. The complexes are isostructural with RSRS configurations at the phosphorus atoms. The ligand is co-ordinated by four nitrogen atoms in a plane and by four phosphinate oxygen atoms in a parallel plane. The planes form a twisted square prismatic co-ordination sphere. A molecule of water capping the O4 plane completes the co-ordination sphere of both ions. Solution properties of the complexes were investigated by 1H and 31P NMR. In solution six possible isomers with different configurations on phosphorus atoms are in equilibrium. The most abundant shows the RRRS configuration. A dynamic behavior similar to lanthanide complexes of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid is not observed. The NMR as well as luminescence measurements show that no water molecule is co-ordinated directly to the lanthanide ions in solution. The ions Li+and Na+ form stable ion pairs with the complexes in methanol-d4 solution as confirmed by the lanthanide induced shift of 7Li and 23Na resonances in the presence of paramagnetic lanthanide ions. The ion pairs are not stable in aqueous solution. The alkali metal ion is located close to fourfold magnetic axes of the complexes above the oxygen atoms and between the phenyl rings. Luminescence spectra of [LnL1]–, Ln = Eu or Tb, indicate low symmetry of the species and co-ordination number 8.

Physical, chemical, and mineralogical evidence for magmatic fluid migration within the Capitan pluton, southeastern New Mexico

The ≈300 km 3 , 28.8 Ma granitic Capitan pluton, located in southeastern New Mexico, was the source of high-temperature (up to 600°C), high-salinity (up to 80 wt%) fluids that formed small REE-bearing zones of mineralization in the pluton carapace. Erosional dissection of the pluton reveals zones in the granite that are characterized by bubble-like void spaces and fissures. These could be interpreted, on one hand, as original magmatic porosity resulting from the interconnection and/or coalescence of bubbles of magmatic volatile phase, or on the other hand, as void spaces resulting from postcrystallization dissolution. These porous zones grade upward into the brecciated portions of the pluton carapace that hosts mineralization. The zones are planar features, traceable across valleys, and even between adjacent valleys on the pluton9s flanks. The orientation of the zones is roughly concentric with the exposed shape of the pluton. Chemical analyses of samples collected across a porous zone reveal that some elements, including Fe, Al, Rb, and Sr are depleted in the entire area surrounding the porous zone, whereas Si, Na, Ba, and Ta are enriched. Other elements, including K, Sb, Zn, Zr, a number of rare earth elements (REE), Pb, and Th, exhibit a slight to strong depletion surrounding the porous zone and a strong enrichment roughly centered on the zone itself. Abundance of high-salinity fluid inclusions in igneous quartz is high within the entire 2.5-m-wide zone but is significantly higher in the central porous zone. The chemical and fluid inclusion abundance patterns could be produced by a two-step process with the wide depletion caused first, by fractionation of elements from the melt into a volatile phase at the time that volatile exsolution first occurred. This could be followed by the superimposed enrichment pattern for certain elements caused by deposition of these elements from trace-element-rich fluids, which evolved in a more central, deeper part of the pluton and were transported along the same zone (although now more crystallized) of fluid migration established earlier, depositing minerals as it cooled. Textural, petrographic, and geochemical evidence suggest that volatiles may have exsolved during crystallization, coalescing into bubble-rich zones that enhance the efficiency of volatile transport.

Preparation of R-α′-β′-Sialons (R = Sm, Gd, Dy, Y and Yb) by pressureless sintering

Abstract R-α′-β′-Sialon (R = Sm, Gd, Dy, Y and Yb) compositions with a nominal 1 : 1 weight ratio of α′ and β′ have been prepared. Nearly fully dense α′-β′-sialon materials were obtained by pressureless sintering at 1800°C. The phase distribution was determined by both X-ray diffraction and image analysis of SEM micrographs. The atomic number of rare earth elements has a significant effect on the phase distribution. With increasing atomic number the ratio α′ (α′ + β′) increases and the amount of liquid phase decreases. The influences of rare earth elements on the microstructure and mechanical properties were also studied.

Isopropyl-3-Pentadecylphenyl Phosphoric Acid - A New Reagent for Liquid-Liquid Extraction and Separation of Rare Earths

Abstract A new reagent isopropyl-3-pentadecylphenyl phosphoric acid (IPPA = HR) was synthesized from cardanol [I-37, 300-39-5] and was used to investigate the extraction behaviour of lanthanum(III), europium(III) and lutetium(III) from HCl and HClO4 solutions into toluene. The species extracted were found to be Ln(HR2)3 (where Ln = La(III) or Eu(III) or Lu(III). The extraction behaviour of above lanthanides has also been compared with yttrium and other rare earths. It was observed that the extraction increases with increase of atomic number of rare earths. In addition the extraction efficiency of IPPA has been compared with well known acidic organophosphorous extractants like di-2-ethylhexyl phosphoric acid (DEHPA) and 2-ethylhexyl-mono-2-ethylhexyl phosphoric acid (EHEHPA).

Electrochemical reduction of rare-earth chelates with certain ?-diketones

Chelates of a number of lanthanides (Pr, Eu, Tb, Dy, Er, Tm, Yb) and certain other metals (Cu, Ni, Co, Tl) with the β-diketones dipivaloylmethane and trifluoroacetylcamphor are reduced electrochemically for the first time in aprotic medium (DMF). The nature of the lowest unoccupied molecular orbital, into which the first electron enters, is demonstrated to be centered on the ligand and not the metal. A difference is observed in the polarographic behavior of the cerium subgroup complexes (Pr, Eu), which are reduced in one step, and those of the yttrium subgroup, which exhibit two waves (Tb, Er, Yb) of a distinctly doubled wave (Tm, Dy).

Optical absorption of rare-earth-doped BeF2 glasses

BeF2 glasses are potentially useful materials for light transmission in the near infrared region of the spectrum. While the intrinsic attenuation of BeF2 is thought to be much lower than silica, the optimum wavelength will be further in the infrared, near 2.1 μ. In this spectral region impurities other than transition metals may be important—rare earths, for example. The data required to estimate the contributions to attenuation are normally not available; hence it is the purpose of the present work to provide that information. Using a binary BeF2/ThF4 glass, the optical absorption spectra of a number of rare earths are measured. The experimental procedures, optical spectra, and absorption strength are described.

Electronic Structure and4f-Hole Lifetime in Rare-Earth Borides

X-ray photoelectron spectra of rare-earth borides exhibit systematic variations of the $4f$ lifetime width with the rare-earth number across the series, with the $4f$ binding energy, and with the number of boron neighbors. Valence band spectra and theoretical band structures make it possible to understand these observations in terms of an interatomic Auger process, here a $5d\ensuremath{\rightarrow}4f$ recombination, with simultaneous excitation of an electron-hole pair from boron $2sp$ states.

Electron density calculations derived from the energy balance equation in a d.c. arc plasma burning in air

The Elenbaas-Heller equation was used to calculate the spatial distribution of electron densities ( n e(itR.z) ) in a d.c. arc plasma burning in air at atmospheric pressure. Uranium, thorium, zirconium and a number of rare-earths were introduced as oxides into the plasma. The temperature and the electric field gradients were measured axially and radially. Electron densities were then derived from the calculated mean electrical conductivity ( σ ( R.z) ). The resulting electron density values were compared with values derived from Saha's equation for ionization processes.

Crystallographic shear relations between the structure types α-UO3, CaF2, La2O3and NaCl and a correlation of some lanthanide and actinide oxide structures

When the α-UO3, La2O3 and NaCl structure types are idealized by a topological distortion involving only an extension or contraction of the hexagonal c axis (cubic [111]) it is clear that they are related to each other, and to the CaF2 type, by crystallographic shear. A number of lanthanide and actinide oxide structures are of these types, or derived superstructure types containing ordered anion `vacancies' or `interstitial' anions. The structural relations suggest possible reduction mechanisms.

Acidic organophosphorus extractants—IX extraction of some lanthanides by means of dibutylphosphoric acid from strong acidic medium

The distribution of 141Ce, 152,154Eu, 160Tb and 168Tm between aqueous solution in perchloric, nitric or hydrochloric acids and dibutylphosphoric acid solution in benzene was studied. Beyond a certain limiting concentration of the mineral acid in the aqueous phase, a change of the extraction mechanism takes place, the Me X 3(HDBP) 3 complexes being extracted by the solvation mechanism ( X = ClO 4, NO 3, Cl). This extraction mechanism is independent on the initial concentration of hydrogen ions and on the atomic number of rare earth elements.

THE EXTRACTION OF THORIUM AND SOME LOWER LANTHANIDE NITRATES BY DIBUTYL BUTYL PHOSPHONATE

The distribution of thorium and a number of lanthanides between nitric acid and solutions of dibutyl butyl phosphonate in odorless kerosene has been examined as a function of the aqueous nitric acid concentration. Experiments were conducted at trace metal concentration using radioisotopes. Separation factors (denoted by S and defined as the ratio of the distribution coefficients, K, for two metal species) have been measured for some lanthanide–lanthanide couples and also for some thorium–lanthanide couples. Results indicate that separation factors between successive lanthanides (given by S = KZ+1/KZ) at the lower end of the rare-earth series are superior to those obtained with either tributyl phosphate (TBP) (D. Scargill et al. J. Inorg. & Nuclear Chem. 4, 304 (1957)) or trioctyl phosphine oxide (TOPO) (J. M. Schmitt. Oak Ridge National Laboratory. Unpublished data), but as Z increases, SDBBP ~STBP > STOPO. For thorium–lanthanide couples, S′DBBP > S′TBP. Measurements over a range of extractant concentrations indicate that the lanthanides are extracted as trisolvates.

A Study on Anion Exchange aud Amine Extraction of Rare Earth Elements in Nitric Acid

Abstract The amine extraction of rare earth elements in nitric acid is compared with anion exchange and TBP extraction with respect to the increase or decrease in Kd value with increasing atomic number of rare earth elements. Concerning the relationship between distribution coefficient and atomic number of rare earth element, a similar trend is observed in anion exchange and amine extraction. The distribution coefficient decreases with increase in the atomic number. In TBP extraction, however, the corresponding value increases with increasing atomic number. It seems that the mechanism of amine extraction for rare earth element is similar to that of anion exchange.

Is Proto-Oxygen the Principal Constituent of the Atoms?

As from Moseley's experiments we know the number of rare-earth elements between La and Ta to be 15, the mean difference between atomic weights is, from Mg on, for 6 atomic numbers, 16 exactly. So for Mg (Atw. 24, N 12) and Th (Atw. 232, N 90) we get (232 − 24)/16 = (90 − 12)/6;=13. Between U and Nt this difference of 238 − 222 = 16 is known to be a difference of 4α + 2β particles. But if the α particle is the real constituent of the atoms, 4α + 2β is the inner part of the oxygen atom (the additional 6 β particles being electrons of valency). That atomic weights are not twice the atomic numbers would be due thus to the formation of α4β2 = θ particles, or proto-oxygen, within the nucleus, and radio-activity should be the disintegration of these particles into their constituents. It may be remarked that α4β2= θis similar to H4+β2 (which might be the formula for the α particle).

Intra-atomic Charge and the Structure of the Atom

I AM very grateful to Mr. Soddy (NATURE, December 4, p. 399) that in accepting in principle the hypothesis that the intra-atomic charge of an element is determined by its place in the periodic table, he directed attention to the possible uncertainty of the absolute values of intra-atomic charge and of the number of intra-atomic electrons. Surely the absolute values depend on the number of rare-earth elements; but if to the twelve elements of this series, the international table contains between cerium and tantalum, the new elements (at least four) discovered by Auer von Welsbach in thulium (Monatshefte fur Chemie 32, Mai, S. 373), further keltium, discovered by Urbain (Comptes rendus d. l'Acad. des Sciences, 152, 141–3), and an unknown one for the open place between praseodymium and samarium be added, this long period, too, becomes regular. Moreover, if only twelve instead of eighteen elements existed here, the ratio of the large-angle scattering per atom divided by M2 is no longer constant, the values for copper, silver, tin, platinum, and gold then being 1.16, 1.15, 1.19, 1.26, and 1.24 respectively, instead of 1.16, 1.15, 1.19, 1.17, and 1.15; and the same holds for the following relation concerning the number of intra-atomic electrons.