Yu. A. Teterin

X-ray photoelectron studies of Ca, Sr and Ba and their oxides and carbonates

Abstract X-ray photoelectron studies were carried out for bulk samples of the metals Ca, Sr and Ba, their oxides formed on the metal surfaces and their carbonates in the energy range 0–1000 eV. The dependence of oxygen O1s electron binding energy E b (eV) on the inverse metal-oxygen distance (1/ R M−0 , nm −1 ) was found for the oxides MO (M = Mg, Ca, Sr, Ba) to be E b (O1s) = 2.27/ R M−0 + 519.4 eV, where E b values are given relative to E b (C1s) = 285.0 eV. It was shown that fine structure features, attributed to the “giant Coster-Kronig fluctuation”, in the spectra of Ba4p electrons vary a little on going from the metal to the oxide and the carbonate. Sensitivity factors k which are needed for elemental quantitative analysis by the equation n 1 / n 2 = ( I 1 / I 2 ) k were measured for the oxides and carbonates studied, where n i represents the element concentration and I i represents the line intensity ( i = 1, 2).

A study of synthetic and natural uranium oxides by X-ray photoelectron spectroscopy

Synthetic and natural uranium oxides UOx (2≦×≦3) have been studied with X-ray photoelectron spectroscopy (XPS) to determine the phase composition and content of uranium ions in uraninites with a varying degree of oxidation. A strong hybridization of U6p and O2s orbitals has been found which permits a quantitative assessment of the U-O bond lengths. The values of such bonds in some substances have been found to be smaller than those in synthetic U(VI) oxide. The oxides U2O5 and U3O8 contain two types of uranium ions with a varying degree of oxidation.

The XPS spectra of cerium compounds containing oxygen

Abstract The fine structure of XPS lines of electrons of valent and inner subshells in cerium oxide CeO2, orthoniobate CeNbO4, ortomethoxibenzoateCeL3(L = C6H4OCH3COOH−) and diphenylacetateCeL′3·2H2O(L′ = (C6H5)2CHCOO−) was studied in the range of electron binding energies from 0 up to 1350 eV. Its comparison with trifiuoride CeF was carried out in order to determine the mechanism of such structure occurrence and the oxidation degree of cerium ions in the compounds. It was established that the structure Ce(II) has more in common with the studied compounds and differs essentially from that of the Ce(IV) in cerium oxide CeO2. It allows one to determine the oxidation degree of the cerium in the compounds on the basis of the values of the XPS line parameters. On the basis of experimental data it was supposed that the structure, for example of the Ce3d-electron spectrum in CeO2, is connected with final electronic states of cerium ion: Ce3d94f0, Ce3d94f1VMO−1 and Ce3d95s1(5p5)4f0ns(np). It is worth noting that the unique final state formally designated as Ce3d95s1(5p5)4f0ns(np) is not the state with the additional hole on the atomic Ce5s(5p) orbital, but that of on inner valent molecular orbital of a1g (t1u) type for the cluster CeO812− of Oh symmetry group, generally consisting of Ce5s(5p), O2s and O2p atomic orbitals of neighbouring Ce and O atoms in CeO2.

Auger and X-ray photoelectron spectroscopy study of the density of oxygen states in bismuth, aluminium, silicon and uranium oxides

The correlation of relative partial electron density at the oxygen ions with the intensity of Auger O KLL lines in Bi2O3, Al2O3, SiO2 and UO2 has been determined by Auger and X-ray photoelectron spectroscopic methods. The dependence of the relative intensities of Auger O KL2-3L2-3 and O KL1L2-3-lines was characterized from the binding energy of O 1s electrons. The electron density of the outer valence levels of oxygen increases as the relative intensities of Anger OKL2-3L2-3 and O KL1L2-3-lines increase. The fine structure observed in the O KL1L2-3 Auger and the O 2s XPS spectra has been explained by the formation of inner valence molecular orbitals (IVMO) from the interaction of electrons of the O 2s and filled metal ns shells.

Electronic valence band structure of high-Tc superconductors: X-ray emission spectroscopy study

Abstract The distribution of the electronic density of O 2p and Cu 3d states in a series of bismuthates and cuprates has been studied by X-ray emission spectroscopy (XES). It has been found that in BaPb 1- x Bi x O 3 , La 2- x Sr x CuO 4 and YBa 2 Cu 3 O 7- x , a high-energy shift of the O Kα spectrum in both photon energy and Fermi level-related scales occurs during the transition from semiconducting to superconducting phase. This shift is explained by the redistribution of 2p states of apical oxygen atoms. The binding energy of Cu 3d states for YBa 2 Cu 3 O 6.2 is rather low in contrast to that for YBa 2 Cu 3 O 6.9 because of the presence of monovalent copper atoms in the semiconductor as a result of oxygen depletion of Cu-O chains. A correlation between T c and the energy localization of the O 2p band relative to E F has been observed in a series of cuprates, the superconducting transition temperature of which varies from 35 to 125 K. On increasing T c , O 2p states shift towards the Fermi level while the binding energy of Cu 3d states insignificantly rises.

Sorption of Np(V), Pu(V), and Pu(IV) on colloids of Fe(III) oxides and hydrous oxides and MnO2

AbstractSorption of Np(V), Pu(V), and Pu(IV) on colloids of synthetic goethite (α-FeOOH), hematite (α-Fe2O3), maghemite (γ-Fe2O3), and amorphous MnO2 was studied over wide ranges of solution pH and ionic strength by solvent extraction and X-ray photoelectron spectroscopy (XPS). Plutonium(V) is reduced upon sorption on α-FeOOH, but not on α-Fe2O3 and γ-Fe2O3. On the MnO2 surface, Pu occurs as Pu(VI). From the pH dependences of the actinide sorption, the equilibrium constants of the reactions of Np(V)O2+ and Pu(V)O2+ with the surface hydroxy groups of the investigated colloid particles and a set of the equilibrium constants of the reactions of Pu(IV) hydroxo complexes with α-FeOOH were obtained. If no redox reactions occur on the surface of the colloid particles, these constants decrease in the order

Interaction of neptunyl with goethite (α-FeOOH), maghemite (γ-Fe2O3), and hematite (α-Fe2O3) in water as probed by X-ray photoelectron spectroscopy

K_{MnO_2 } > K_{\alpha - FeOOH} > K_{\alpha - Fe_2 O_3 } \sim K_{\gamma - Fe_2 O_3 }

X-ray photoelectron study of Te-W-O and Te-W-La-O glasses

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