The Fine Structure of the X-ray Absorption Edge in the K-Series of Argon and its Possible Interpretation

Nature ◽  
1926 ◽  
Vol 117 (2947) ◽  
pp. 586-587 ◽  
Author(s):  
D. COSTER ◽  
J. H. VAN DER TUUK
2002 ◽  
Vol 57 (5) ◽  
pp. 277-280 ◽  
Author(s):  
Yoshihiro Okamoto ◽  
Haruhiko Motohashi

The local structure of motlen ZrCl4 in LiCl-KCl eutectic was investigated by using an X-ray absorption fine structure (XAFS) of the Zr K-absorption edge. The nearest Zr4+-Cl- distance and coordination number from the curve fitting analysis were (2.51±0.02) Å and 5.9±0.6, respectively. These suggest that a 6-fold coordination (ZrCl6)2- is predominant in the molten mixture.


2007 ◽  
Vol 22 (2) ◽  
pp. 122-125 ◽  
Author(s):  
T. N. Blanton ◽  
D. R. Whitcomb ◽  
S. T. Misture

Silver K edge extended X-ray absorption fine structure (EXAFS) spectroscopy of films containing silver behenate (AgBeh) in the unprocessed, fully processed, and step-processed states has been performed. The results of the EXAFS analysis indicate that the intensity for the real-space peak for the Ag-O distance (∼2.3 Å) decreases while the real-space peak for the Ag-Ag distance (∼2.9 Å) grows with increasing thermal processing of the film. The changes observed in the real-space EXAFS signal indicate the growth of metallic silver at the expense of AgBeh. The X-ray absorption near-edge spectroscopy (XANES) portion of the signal shows that the absorption edge position varies stepwise, with unprocessed films and pure AgBeh having an edge location at 25 506 eV, films processed from steps 1 through 10 have an absorption edge at 25 508 eV, and the fully processed film has an edge location at 25 512 eV.


1995 ◽  
Vol 10 (8) ◽  
pp. 2091-2105 ◽  
Author(s):  
Jeffrey R. Lince ◽  
Michael R. Hilton ◽  
Arun S. Bommannavar

Solid lubricant films produced by cosputtering metals with MoS2 and by forming metal/MoS2 multilayers are being planned for use in the next generation of solid lubricated devices on spacecraft, including gimbal and sensor bearings, actuators, and sliding electrical contacts. The films exhibit increased densities and wear lives compared to films without additives, but the mechanism of density enhancement is not well understood. The extended x-ray absorption fine structure (EXAFS) technique is ideal for elucidating the structure of these poorly crystalline films. We analyzed MoS2 films cosputtered with 0, 2, and 10% Ni, as well as Ni/MoS2 and Au(Pd)/MoS2 multilayer films. The results obtained at the Mo-K absorption edge showed that the metal-containing films comprised predominantly the same nanocrystalline phases present in similar films without added metals: pure MoS2 and a MoS2−xOx phase. MoS2−xOx is isostructural with MoS2, with O atoms substituting for S atoms in the MoS2 crystal lattice. For all Ni-containing films, EXAFS data obtained at the Ni-K absorption edge showed that the Ni had not chemically reacted with the MoS2−xOx and MoS2, but formed a disordered NiOx phase. However, Ni-cosputtered films showed decreasing Mo-Mo bond lengths in the MoS2−xOx phase with increasing Ni content, probably due to preferential oxidation of Ni compared to MoS2. EXAFS of these Ni-cosputtcred films showed only a small decrease in short-range order with Ni content, while x-ray diffraction showed a concurrent large decrease in long-range order. The results indicate that film densification in Ni-cosputtered films is caused by NiOx formation at the edges of nucleating MoS2−xOx/MoS2 crystallites, limiting the crystallite size attainable within the films.


1993 ◽  
Vol 307 ◽  
Author(s):  
Ingrid J. Pickering ◽  
Michael Sansone ◽  
James Marsch ◽  
Graham N. George

ABSTRACTDiffraction anomalous fine structure (DAFS) is the fine structure in the intensity of an X-ray diffraction peak in the vicinity of an absorption edge. DAFS is measured by monitoring the intensity of a diffraction peak as a function of the incident X-ray energy as it is scanned through an absorption edge. It combines the short range structural sensitivity of X-ray absorption spectroscopy with the long range periodicity of X-ray diffraction, and can provide structural information which is not available from these techniques alone, or in combination. We present a methodology which allows extraction of a specific X-ray absorbance spectrum from the DAFS spectrum, and illustrate it for KMnO4. We also demonstrate the ability of DAFS to separate the contributions to the X-ray absorption spectrum of the tetrahedral and octahedral cobalt sites in the spinel Co3O4.


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