Role of Spin-Orbital Splitting of 5f-Orbitals of Uranium Atom in the Formation of Its Chemical State

2003 ◽  
Vol 802 ◽  
Author(s):  
Yuri F. Batrakov ◽  
Andrey G. Krivitsky ◽  
Elena V. Puchkova
Keyword(s):  
Chemical Shifts ◽  
Uranium Atom ◽  
Atomic Charge ◽  
Uranium Oxides ◽  
Spin Doublet ◽  
Spin Orbital ◽  
X Ray ◽  
Hartree Fock ◽  
Uranium Oxidation

ABSTRACTChemical shifts (ChSh) of nine emission lines of the uranium L-series in uranium oxides UO2+x (x=0−1) with respect to UO2 were studied by using a precise crystal-diffraction X-ray spectrometer and the changes in energy of spin-orbital splitting (SOS) − Δδnl± of inner nl-orbitals of the uranium atom were calculated from the data of ChSh of spin-doublet lines. For UO2+x oxides, a linear decrease in Δδnl± values with increasing degree of uranium oxidation was found.On the basis of the comparison of experimental Δδnl± values with Dirac-Hartree-Fock atomic calculations, it was concluded that the observed variations in Δδnl± values are due to the redistribution of electron and spin density between the 5f7/2- and 5f5/2-levels of the fine structure of the uranium atom without changes in atomic charge state.

Effect of the chemical state of uranium atom on the energy of spin-orbital splitting of its inner orbitals

2004 ◽  
Vol 92 (2) ◽  
Author(s):  
Yuri F. Batrakov ◽  
Andrey G. Krivitsky ◽  
Oleg V. Pospelov ◽  
Elena V. Puchkova
Keyword(s):  
Chemical Shifts ◽  
Uranium Atom ◽  
Chemical State ◽  
Emission Lines ◽  
Spin Orbital

SummaryChemical shifts (ChSh) of nine emission lines of the uraniumOn the basis of the comparison of experimental Δ

The role of Hartree–Fock exchange in the simulation of X-ray absorption spectra: A study of photoexcited

2013 ◽  
Vol 580 ◽  
pp. 179-184 ◽  
Author(s):  
G. Capano ◽  
T.J. Penfold ◽  
N.A. Besley ◽  
C.J. Milne ◽  
M. Reinhard ◽  
...  
Keyword(s):  
Absorption Spectra ◽  
X Ray ◽  
Hartree Fock ◽  
X Ray Absorption

Dirac-fock calculations of scattering factors and mean inner potentials for neutral and ionised atoms

1993 ◽  
Vol 51 ◽  
pp. 1202-1203
Author(s):  
David Rez ◽  
Peter Rez
Keyword(s):  
Solid State ◽  
Electron Scattering ◽  
Atomic Charge ◽  
X Ray ◽  
Charge Densities ◽  
Hartree Fock ◽  
Atomic Scattering

Tables of X-ray and electron scattering factors are essential for programs that calculate diffraction intensities or simulate images. These tables are calculated from atomic charge densities derived from Hartree Fock programs for atoms. The most frequently used results are those due to Doyle and Turner who used Coulthard's relativistic Hartree Fock program. They did not calculate scattering factors for all elements and other results using different programs were used to complete the tables given in the International Tables for Crystallography. As microscopy and diffraction become more quantitative it has become important to reexamine the calculation of atomic scattering factors using more recent Hartree Fock codes to quantify more precisely differences due to solid state effects. We also feel it is desirable to calculate all naturally occuring elements, and their common ionised states, using the same program.The charge densities were calculated using the Multi-Configuration Dirac-Fock code of Grant et al.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

The role of silicon in forages: A quantitative X-Ray study

1987 ◽  
Vol 45 ◽  
pp. 416-417
Author(s):  
Janet H. Woodward ◽  
D. E. Akin
Keyword(s):  
Sodium Acetate ◽  
Dry Matter ◽  
Acetate Buffer ◽  
Plant Tissues ◽  
Sodium Acetate Buffer ◽  
X Ray ◽  
Dry Matter Digestibility ◽  
Percent Composition

Silicon (Si) is distributed throughout plant tissues, but its role in forages has not been clarified. Although Si has been suggested as an antiquality factor which limits the digestibility of structural carbohydrates, other research indicates that its presence in plants does not affect digestibility. We employed x-ray microanalysis to evaluate Si as an antiquality factor at specific sites of two cultivars of bermuda grass (Cynodon dactvlon (L.) Pers.). “Coastal” and “Tifton-78” were chosen for this study because previous work in our lab has shown that, although these two grasses are similar ultrastructurally, they differ in in vitro dry matter digestibility and in percent composition of Si.Two millimeter leaf sections of Tifton-7 8 (Tift-7 8) and Coastal (CBG) were incubated for 72 hr in 2.5% (w/v) cellulase in 0.05 M sodium acetate buffer, pH 5.0. For controls, sections were incubated in the sodium acetate buffer or were not treated.

Microstructure and reactivity of small metal particles: The role of Ce additives

1992 ◽  
Vol 50 (1) ◽  
pp. 318-319
Author(s):  
L.D. Schmidt ◽  
K. R. Krause ◽  
J. M. Schwartz ◽  
X. Chu
Keyword(s):  
Atmospheric Pressure ◽  
Noble Metals ◽  
Mixed Oxides ◽  
Catalytic Properties ◽  
Chemical Shifts ◽  
Catalytic Converter ◽  
Structural Evolution ◽  
Single Particles ◽  
Small Metal Particles

The evolution of microstructures of 10- to 100-Å diameter particles of Rh and Pt on SiO2 and Al2O3 following treatment in reducing, oxidizing, and reacting conditions have been characterized by TEM. We are able to transfer particles repeatedly between microscope and a reactor furnace so that the structural evolution of single particles can be examined following treatments in gases at atmospheric pressure. We are especially interested in the role of Ce additives on noble metals such as Pt and Rh. These systems are crucial in the automotive catalytic converter, and rare earths can significantly modify catalytic properties in many reactions. In particular, we are concerned with the oxidation state of Ce and its role in formation of mixed oxides with metals or with the support. For this we employ EELS in TEM, a technique uniquely suited to detect chemical shifts with ∼30Å resolution.

Pathophysiological function of the mitochondria as a calcium reservoir: Quantitative x-ray microanalysis

1990 ◽  
Vol 48 (2) ◽  
pp. 164-165
Author(s):  
K. Teraoka ◽  
N. Kaneko ◽  
Y. Horikawa ◽  
T. Uchida ◽  
R. Matsuda ◽  
...  
Keyword(s):  
Bolus Injection ◽  
Contact Method ◽  
X Ray

The aim of this study was to elucidate the role of the mitochondria as a store of calcium(Ca) under the condition of pathophysiological Ca overload induced by a rise in extracellular Ca concentration and the administration of isoproterenol.Eight rats were employed, and hearts were perfused as in the Langendorff method with Krebs-Henseleit solution gassed with 95% O2 and 5% CO2. Tow specimens were perfused with 2mM Ca for 30 min, and 2 were perfused with 5.5 mM Ca for 20 min. 4 specimens were perfused with 2 mM Ca for 5 min, and of these 4, 2 were infused with 10-7 mM/kg/min. isoproterenol for 5 min, and 2 were given a bolus injection of 3 x 10-7 mM isoproterenol. After rapid-cryofixation by the metal-mirror contact method with a Reichert-Jung KF80/MM80, and cryosectioning at -160 to -180° C with a Reichert-Jung Ultracut Fc-4E, ultrathin specimens (100nm) were free-ze-dreid for several hours at 10-5 Torr in the JEOL FD 7000, and mitochondrial Ca was determined by quantitative x-ray micranalysis (JEOL 1200EX, LINK AN 10000S).

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