Dale L. Perry

Determination of 207Pb2+ chemical shift tensors from precise powder lineshape analysis

207Pb solid state NMR powder spectra at 296 K are presented for PbSO4, PbMoO4, PbCrO4, PbCO3, PbTiO3, PbZrO3, Pb(NO3)2, Pb(SCN)2, and PbS. Analysis for principal values of the anisotropic chemical shift tensors of the generally very broad spectra included the frequency dependent excitation of the pulse sequence used. Commonly used solid and liquid secondary shift standards for lead were studied with high precision as a function of temperature between 295 K and 315 K to establish a clean 207Pb shift scale. Errors in the existing literature are discussed.

An x-ray photoelectron and electron energy loss study of the oxidation of lead

Lead–oxygen compounds and the exposures of clean polycrystalline Pb0 to O2, H2O, and air at various temperatures have been studied with x‐ray photoelectron (XPS) and electron energy loss (EELS) spectroscopies. Results indicate that the shape of the Auger O KVV lines and EELS are sufficiently different to distinguish PbO, PbO2, Pb3O4, and carbonate–hydroxide. Differences in the EELS spectra indicate that orthorhombic PbO is formed on clean Pb0 exposed to dry O2 at temperatures below the melting point of Pb0, and tetragonal PbO is formed at or above its melting point.

Surface study of HF- and HFH2SO4-treated feldspar using Auger electron spectroscopy

Auger electron spectroscopy has been used to study K-feldspar that has been reacted with both aqueous 10% HF and a 50% mixture of a 10% HF/0.1 N H/sub 2/SO/sub 4/ solution. In the feldspar/HF system, the resulting feldspar surface was shown to have been fluorinated; depth profiling, using argon ion sputtering showed the fluorination to have occurred substantially into the mineral bulk. In the feldspar/HF/H/sub 2/SO/sub 4/ system, the resulting surface contained both fluorine and sulfur. The fluorination had again penetrated into the bulk, but the sulfur could be removed with mild argon ion sputtering. The Al/F signal ratio was much lower on the feldspar surface treated with the 10% HF/0.1 N H/sub 2/SO/sub 4/ solution than the feldspar surface treated with the weaker 10% HF acid solution.

Imidazolium tetrachlorodioxouranate(VI), [C3N2H5+]2[UO2Cl4]2−

Abstract The crystal and molecular structure of imidazolium tetrachlorodioxouranate(VI) has been determined by X-ray diffraction methods. The crystals, obtained by reacting imidazole and UO 2 Cl 2 ·3H 2 O in hydrochloric and maintained at pH = 2.5–;3.0, are monoclinic, P2 1 /n, with cell dimensions a = 9.385(5) A, b = 10.891(5) A, c = 6.966(4) A, β = 104.56(5)° and V = 722 A 3 . For Z = 2 the calculated density is 2.53 g/cm 3 . The structure was refined to a conventional R factor of 0.034 using 1494 data where F 2 > σ(F 2 ). The [UO 2 Cl 4 ] −2 anion is octahedral with UO distance of 1.770 A and UCl distances of 2.692 and 2.657 A. The imidazolium cation is planar.

Raman studies of uranyl nitrate and its hydroxy bridged dimer

Abstract In this paper, the authors report Raman spectra obtained on imidazolium di-μ-hydroxybis[dioxobis-(nitrato)uranium(VI)], (UO2(NO3)2(OH))2.2C3H5N2 (IUNH). An assignment of the Raman bands is made by comparing the spectrum of IUNH with those of uranyl nitrate hexahydrate (UNH) and imidazole (IMID). The electron charge transfer from the imidazole ring to the uranyl ion has been empirically determined.

Luminescence studies of lanthanide oxides: I. Thermal and hydration effects on the metal ion site symmetry in Europium oxide catalysts

Abstract High-resolution luminescence spectroscopy has been used to study the site symmetry of Eu(III) ions in Eu 2 O 3 prepared under conditions suitable for catalytic use. It was found that the Eu(III) site symmetry was a sensitive function of the pretreatment procedure, and it proved possible to determine the number of spectroscopically nonequivalent Eu(III) ions in the oxide material from an analysis of the fine structure within the emission bands. The site symmetry is altered primarily by thermal effects, and hydration of the oxide is not found to induce large changes in site symmetry.

Spectroscopic studies of the thermal decomposition products of hydrated cerous oxalate

Abstract The thermal decomposition of hydrated cerous oxalate has been studied by means of thermogravi- metry, differential scanning calorimetry, infrared spectroscopy, powder X-ray diffraction, magneto- chemistry, and X-ray photoelectron spectroscopy. Materials were isothermally calcined at appropriate temperatures and then subjected to a sertes of spectroscopic investigations. It was found that the dehydration and oxalate decomposition steps were effectively merged into a concerted decomposition when isothermal heating conditions were used. The only product identifiable by powder X-ray diffraction in the calcination products was ceric oxide, CeO2. Magnetochemical data demonstrated that one could not form analytically pure ceric oxide in the temperature range studied and that substantial amounts of amorphous cerlum(III) products were also obtained. These observations were corroborated by detailed X-ray photoelectron spectroscopic studies of the materials.

Photophysical studies of uranyl complexes: VIII. Luminescence spectra of UO2SO4 · 312H2O and two polymorphs of bis(urea) uranyl sulfate

Abstract The photoluminescence spectra of hydrated and anhydrous uranyl sulfates have been studied under conditions of high resolution at cryogenic temperatures. All uranyl sulfate systems were found to yield nonequivalent spectra: the energies for the electronic and vibronic origins were found to vary with the system, and certain uranyl vibrational frequencies exhibited a dependence on environment. These differences must reflect the various ways in which the uranyl centers are linked by the bridging sulfate groups, as this linking is the main difference between the various structures.

Photophysical studies of uranyl complexes 5. Luminescence spectrum of K4UO2(CO3)3

The photoluminescence of K4UO2(CO3)3 has been studied under conditions of high resolution at cryogenic temperatures. The origin corresponding to the pure electronic transition was located at 4774 A (20945 cm−1), and it was found that the totally symmetric uranyl stretching mode was coupled to this transition. A progression of four band systems thus resulted, and from an examination of the energies of corresponding peaks in each system, a value of 813 cm−1 for the U-O stretching mode was determined. Two lattice modes (34 and 80 cm−1) and two molecular vibrational modes (205 and 276 cm−1) were also found to couple with the pure electronic transition, thus yielding approximately 15 major peaks in each band system. The 205 cm−1 vibration corresponded to a CO32− vibration, while the 276 cm−1 vibration was a UO22+ deformation. The low values obtained for the force constant and totally symmetric stretching frequency of the U-O bond suggested that in UO2(CO)34−, the uranium atom is bound in a complex species that may be considered as an intermediate between that of a uranyl (UO22+) and a uranate (UO810−) ion.

A copper/silica catalyst prepared from a monolayer film of copper 2,2′-bipyridine dimer on CabOSil☆

Abstract A dinuclear copper complex was supported as a monolayer film on Cab-O-Sil (2.27 wt% Cu) as a model for Cu/silica. The supported and unsupported metal complexes were characterized by elemental analyses, EPR, SQUID, DRIFTS, and mass spectrometry (EI and FAB) techniques. The magnetic properties and infrared vibrational spectra were altered when the complex interacted strongly with the support by an ion exchange mechanism. The samples were subsequently decomposed by heating in oxygen to produce a highly dispersed supported CuO/silica. This sample was reduced in H2 and the catalyst was exposed to NO and N2O under controlled conditions in separate experiments. The results of these characterizations are discussed in the framework of the theories of catalytic ensembles.