نتایج جستجو برای: exafs
تعداد نتایج: 1685 فیلتر نتایج به سال:
The ABS2 sulphides (A=Cu, or Ag), B=As, Sb, Bi) are a naturally occurring group of minerals, typically found in polymetallic vein deposits. Behind chemically simple, the minerals have a complex structure and undergo several temperature/composition phase transitions. In this study, synchrotron radiation is used to collect Ag, As, Bi, Cu, Cd, Hg and Sb K-edge EXAFS data from a series of synthetic...
Publication 1. A. Manceau et al, “Quantitative Zn speciation in smelter-contaminated soils by EXAFS spectroscopy,” Am. J. Sci. (in press, 2000). Figure 3 (top) Soil samples were taken at several depths from a contaminated site. (bottom) Model compounds derived from polarized-EXAFS data at the ESRF and μ-EXAFS data at the ALS provide a good fit with powder-EXAFS spectra from a soil sample, there...
92 LLE Review, Volume 86 Introduction As part of its participation in the Stockpile Stewardship Program (SSP), LLE is studying the feasibility of using extended x-ray absorption fine structure (EXAFS)1 to characterize the properties of solid materials shocked at moderately high pressures (up to a few megabars). In particular, there is an interest in examining material properties since they affe...
To better understand the extended x-ray absorption fine structure (EXAFS) spectroscopic information obtained for complex materials such as those encountered in Earth sciences, we propose to use the Continuous Cauchy Wavelet Transform (CCWT). Thanks to this method, the EXAFS spectra can be visualized in three-dimension: the wavevector (k), the interatomic distance uncorrected for phase-shifts (R...
The sensitivity of extended X-ray absorption fine structure spectroscopy (EXAFS) for minute structural changes can be enhanced by combination with the modulated excitation approach and making use of phase sensitive analysis. A modulated EXAFS experiment of a reversible periodic Pd to PdO partial oxidation has been simulated in order to understand the effect of the phase sensitive analysis on th...
3, 5, and 12-nm Co nanoparticles were synthesized via thermo-decomposition. Extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) were used to probe the structures of these nanoparticles. Simulations were carried out to compare the EXAFS profiles of three different crystalline phases of Co. The results of EXAFS and XANES suggested that the reactivity ...
The use of principal component (factor) analysis for the interpretation of EXAFS spectra is described. The components derived from EXAFS spectra share mathematical properties with the original spectra. As a result, the abstract components can be analyzed using standard EXAFS methodology to yield bond distances and other coordination parameters. The number of components that must be analyzed is ...
EXAFS (extended X-ray absorption fine structure) investigations are reported concerning the thermal expansion behaviour of silver in an extended range of temperature from 10 K to about 950 K measured in transmission mode. Both the ratio method and an EXAFS fitting procedure were applied to reveal the temperature dependence of EXAFS parameters. Models based on quantum and classical thermodynamic...
This paper reports a three-dimensional EXAFS refinement of the Mo coordination sphere of the FeMoco cluster of the dithionite-reduced MoFe protein from Klebsiella pneumoniae nitrogenase (Kp1) using the 1.6 A-resolution crystallographic coordinates. At this resolution, the positions of the heavy (Fe and S) atoms of the cluster are well determined and there is excellent agreement between the crys...
Tanks to the peculiar sensitivity to correlation of vibrational motion, EXAFS contains original information on thermal properties of crystals. The thermal expansions measured by EXAFS and by Bragg scattering have a different physical meaning. They can be experimentally distinguished by accurate temperature dependent measurements, leading to the evaluation of the perpendicular mean square relati...
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