Showing papers on "Cerium published in 1971"

Heteropolytungstate complexes of the lanthanide elements. Part II. Electronic spectra: a metal–ligand charge-transfer transition of cerium(III)

Abstract: The small nephelauxetic parameters dβ for lanthanide heteropolytungstate complexes show that the Ln–O bond is essentially ionic. The absorption spectra of the EuIII complexes indicate, in each case, site symmetry not higher than tetragonal for the lanthanide; the emission spectra of EuW10O357– and Eu(SiW11O39)211– in the solid state agree best with D2d and D4h microsymmetry respectively. The bands causing the brown colours of the CeIII complexes, whose wavenumbers increase with the CeIV/CeIII redox potential, are assigned to metal–ligand charge-transfer.

Geometry and Infrared Spectra of Matrix‐Isolated Rare‐Earth Halides. I. LaF3, CeF3, PrF3, NdF3, SmF3, and EuF3

Abstract: The infrared absorption spectra (40–800 cm−1) of the trifluorides of lanthanum, cerium, praseodymium, neodymium, samarium, and europium isolated in solid argon, krypton, and nitrogen matrices have been obtained. For LaF3, CeF3, SmF3, and EuF3 only the asymmetric stretching mode and the bending modes were observed; these molecules are assigned a planar configuration. For PrF3 the symmetric and asymmetric stretching modes were observed together with the bending modes; PrF3 is accordingly assigned a pyramidal configuration. At present the spectrum of NdF3 cannot be satisfactorily interpreted, but a number of possibilities are explored. Using a valence force field approximation, force constants have been derived from the measured fundamental frequencies and the infrared‐inactive symmetric stretching frequency of the planar molecules has been estimated. Statistical entropies have also been calculated from the vibrational data and molecular geometries and are compared with third‐law values.

Thermal resistance between powdered cerium magnesium nitrate and liquid helium at very low temperatures

Abstract: Experiments have been performed from magnetic temperatures of 2–20 mK on the effect of minute4He impurities and a magnetic field on the thermal resistance between powdered cerium magnesium nitrate (CMN) and liquid3He. The thermal resistance decreases with decreasingT and increasing small field but is increased dramatically at a givenT by the addition of roughly a monolayer of4He. The resistance is interpreted as resulting from a surface magnetic coupling between CMN and liquid3He.

Electron-Phonon Interaction Effects in the Spectra of Hydrogenated, Deuterated, and Tritiated Crystals of Calcium and Strontium Fluorides Containing Cerium

Abstract: Spectroscopic measurements of cerium-hydride, cerium-deuteride, and cerium-tritide ion pairs in calcium and strontium fluoride crystals are reported. The local-mode spectrum of the hydride ion shows a splitting of the doubly degenerate vibration which is attributed to electron-phonon interaction effects between the cerium $4f$ electronic states and the hydride-ion local-mode phonons. A dipole moment of $1.1e{a}_{0}$ for the hydride ion, where ${a}_{0}$ is the Bohr radius, is postulated to explain the observed local-mode spectrum. The electronic lines of the tetragonal cerium-hydride ion pairs display large isotope shifts of 23. 8 and 35. 1 ${\mathrm{cm}}^{\ensuremath{-}1}$ for hydrogen to deuterium and hydrogen to tritium, respectively. Only the nondegenerate vibration of the hydride ion appears in the vibronic spectrum of the $4f\ensuremath{\rightarrow}5d$ transition of cerium and has a higher frequency when coupled to the cerium-ion $5d$ electronic state than to the $4f$ electronic states. The intensity of these vibronics relative to their parent electronic lines is quantitatively explained on a configuration-coordinate model. Both the electronic line isotope shifts and the vibronic frequency shifts are attributed to electron---local-mode-phonon interaction effects in the cerium-ion $5d$ electronic state. A quantitative model for the electron---local-mode-phonon interaction with point-charge and dipolar interactions between the cerium ion and the hydride ion is set up and includes anharmonic effects. This model successfully explains the vibronic splitting in the local-mode spectrum, the occurrence of only one local-mode frequency in the vibronic spectrum of the cerium $4f\ensuremath{\rightarrow}5d$ transition, and the relative intensity of these lines, but is unsuccessful in explaining the magnitude or sign of the observed isotopic effects. The estimated electronic line isotope shifts are \textonequarter{} the magnitude of the observed shifts and of opposite sign.

The reaction of selected lanthanide carbides with platinum and iridium

Abstract: The dicarbides of yttrium, cerium and erbium have been reacted with platinum and iridium by heating in the range 1000°–1600 °C. The reduction of the carbides leads to the formation of a number of rare-earth platinides and iridides and free carbon. No ternary compounds were found. Ternary diagrams have been deduced. From the reactions, lower limits can be set for free energy of formation of the intermetallic compounds.

Production of ceria

Abstract: Control over physical characteristics of product ceria is provided by a new process in the manufacture of ceria from cerium IV hydroxide. A slurry of the cerium IV hydroxide in water is treated with nitric acid and heated until the pH, which is controlled to be ultimately less than 5.4, reaches a steady value. The slurry thus conditioned is dried to give a dry gel powder.

Etude des oxydes mixtes de lanthanides et de vanadium(V)

Abstract: This work presents a study of the mixed oxides of vanadium(V) and lanthanides by dry methods. The study includes all elements of the rare earth group except cerium and promethium.All orthovanadates of the formula TVO4 were prepared and their lattice parameters redetermined for all lanthanides. New materials were synthesized: lanthanides 4T2O3•V2O5, for elements from samarium to ytterbium the compounds 5T2O3•V2O5• and for praseodymium and neodymium the compounds 6T2O3•V2O5. Identification of these materials was carried out by X-ray diffraction.

Rare earth flouride lubricant for die casting components

Abstract: A rare earth halide preferably a rare earth fluoride such as cerium tri-fluoride or lanthanum tri-fluoride is used as a lubricant for die casting components.

Method of reforming hydrocarbons

Abstract: Method of reforming hydrocarbons which comprises treating a mixture of hydrogen and hydrocarbon at a temperature from 400 DEG C. to 650 DEG C. on a catalyst containing from 0.01 to 5 percent by weight of platinum, from 0.01 to 5 percent by weighth of lead and from 0.01 to 10 percent by weight of at least one member selected from the group consisting of copper, silver, gold, boron, thallium, titanium, zirconium, vanadium, tantalum, manganese, iron, cobalt, nickel, thorium, yttrium, phosphorus, antimony, cerium, scandium, gallium, indium, hafnium and niobium.

Preparation and Properties of Tricyclopentadienyl Cerium (IV) Chloride and Bisindenyl Cerium (IV) Dichloride

Abstract: The reactions of dipyridinium cerium (IV) hexachloride with tetracyclopentadienyl cerium or sodium cyclopentadienide and tetraindenyl cerium or sodium indenide in tetrahydrofuran yield tricyclopentadienyl cerium (IV) chloride and bisindenyl cerium (IV) dichloride. Infrared spectra, thermal stabilities and other characteristics of the compounds have been studied.