Normalization and convergence of x-ray absorption sum rules

2001 ◽  
Vol 63 (9) ◽  
Author(s):  
A. I. Nesvizhskii ◽  
A. L. Ankudinov ◽  
J. J. Rehr
Keyword(s):  
Sum Rules ◽  
X Ray ◽  
X Ray Absorption

Sum rules for polarization-dependent x-ray absorption

1995 ◽  
Vol 51 (2) ◽  
pp. 1282-1285 ◽  
Author(s):  
A. Ankudinov ◽  
J. J. Rehr
Keyword(s):  
Sum Rules ◽  
X Ray ◽  
X Ray Absorption

scholarly journals L-edge sum rule analysis on 3d transition metal sites: from d10to d0and towards application to extremely dilute metallo-enzymes

2018 ◽  
Vol 20 (12) ◽  
pp. 8166-8176 ◽  
Author(s):  
Hongxin Wang ◽  
Stephan Friedrich ◽  
Lei Li ◽  
Ziliang Mao ◽  
Pinghua Ge ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Transition Metal ◽  
Metal Complex ◽  
Sum Rules ◽  
Sum Rule ◽  
X Ray ◽  
Metal Site ◽  
Integrated Intensity ◽  
Rule Analysis ◽  
X Ray Absorption

According to L-edge sum rules, the number of 3d vacancies at a transition metal site is directly proportional to the integrated intensity of the L-edge X-ray absorption spectrum (XAS) for the corresponding metal complex.

X-ray-absorption sum rules injj-coupled operators and ground-state moments of actinide ions

1996 ◽  
Vol 53 (21) ◽  
pp. 14458-14469 ◽  
Author(s):  
Gerrit van der Laan ◽  
B. T. Thole
Keyword(s):  
Ground State ◽  
Sum Rules ◽  
X Ray ◽  
X Ray Absorption ◽  
Actinide Ions

Angular momentum sum rules for x-ray absorption

1998 ◽  
Vol 57 (1) ◽  
pp. 112-115 ◽  
Author(s):  
Gerrit van der Laan
Keyword(s):  
Angular Momentum ◽  
Sum Rules ◽  
X Ray ◽  
X Ray Absorption

Spin-dependent sum rules for X-ray absorption spectra

2004 ◽  
Vol 66 (3) ◽  
pp. 441-447 ◽  
Author(s):  
A. L Ankudinov ◽  
J. J Rehr ◽  
H Wende ◽  
A Scherz ◽  
K Baberschke
Keyword(s):  
Absorption Spectra ◽  
Sum Rules ◽  
X Ray ◽  
X Ray Absorption

X-ray microanalysis of thin specimens in the transmission electron microscope at voltages up to 1000 Kv.

1978 ◽  
Vol 36 (1) ◽  
pp. 540-541
Author(s):  
G. Cliff ◽  
M.J. Nasir ◽  
G.W. Lorimer ◽  
N. Ridley
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Weight Fraction ◽  
Present Series ◽  
Constant Independent ◽  
X Ray ◽  
Transmission Electron ◽  
Series Of Experiments ◽  
Image Position ◽  
X Ray Absorption

In a specimen which is transmission thin to 100 kV electrons - a sample in which X-ray absorption is so insignificant that it can be neglected and where fluorescence effects can generally be ignored (1,2) - a ratio of characteristic X-ray intensities, I1/I2 can be converted into a weight fraction ratio, C1/C2, using the equationwhere k12 is, at a given voltage, a constant independent of composition or thickness, k12 values can be determined experimentally from thin standards (3) or calculated (4,6). Both experimental and calculated k12 values have been obtained for K(11<Z>19),kα(Z>19) and some Lα radiation (3,6) at 100 kV. The object of the present series of experiments was to experimentally determine k12 values at voltages between 200 and 1000 kV and to compare these with calculated values.The experiments were carried out on an AEI-EM7 HVEM fitted with an energy dispersive X-ray detector.

SIGMAL: A Program for Calculating L-Shell lonization Cross-Sections

1981 ◽  
Vol 39 ◽  
pp. 198-199 ◽  
Author(s):  
R.F. Egerton
Keyword(s):  
Cross Sections ◽  
Fortran Program ◽  
Absorption Data ◽  
X Ray ◽  
Atomic Electrons ◽  
Energy Dependent ◽  
Hydrogenic Model ◽  
Electron Energy Loss ◽  
X Ray Absorption ◽  
Shell Ionization

SIGMAL is a short (∼ 100-line) Fortran program designed to rapidly compute cross-sections for L-shell ionization, particularly the partial crosssections required in quantitative electron energy-loss microanalysis. The program is based on a hydrogenic model, the L1 and L23 subshells being represented by scaled Coulombic wave functions, which allows the generalized oscillator strength (GOS) to be expressed analytically. In this basic form, the model predicts too large a cross-section at energies near to the ionization edge (see Fig. 1), due mainly to the fact that the screening effect of the atomic electrons is assumed constant over the L-shell region. This can be remedied by applying an energy-dependent correction to the GOS or to the effective nuclear charge, resulting in much closer agreement with experimental X-ray absorption data and with more sophisticated calculations (see Fig. 1 ).

point-Analysis Using the Extrapolation Method in the Analytical Electron microscope

1990 ◽  
Vol 48 (2) ◽  
pp. 430-431
Author(s):  
Zenji Horita ◽  
Ryuzo Nishimachi ◽  
Takeshi Sano ◽  
Minoru Nemoto
Keyword(s):  
Electron Microscope ◽  
Extrapolation Method ◽  
X Ray ◽  
Absorption Correction ◽  
Point Analysis ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Data Points ◽  
Identical Composition ◽  
X Ray Absorption

Absorption correction is often required in quantitative x-ray microanalysis of thin specimens using the analytical electron microscope. For such correction, it is convenient to use the extrapolation method[l] because the thickness, density and mass absorption coefficient are not necessary in the method. The characteristic x-ray intensities measured for the analysis are only requirement for the absorption correction. However, to achieve extrapolation, it is imperative to obtain data points more than two at different thicknesses in the identical composition. Thus, the method encounters difficulty in analyzing a region equivalent to beam size or the specimen with uniform thickness. The purpose of this study is to modify the method so that extrapolation becomes feasible in such limited conditions. Applicability of the new form is examined by using a standard sample and then it is applied to quantification of phases in a Ni-Al-W ternary alloy.The earlier equation for the extrapolation method was formulated based on the facts that the magnitude of x-ray absorption increases with increasing thickness and that the intensity of a characteristic x-ray exhibiting negligible absorption in the specimen is used as a measure of thickness.

EXELFS Studies of Carbon Fibers

1990 ◽  
Vol 48 (2) ◽  
pp. 72-73
Author(s):  
V. Serin ◽  
K. Hssein ◽  
G. Zanchi ◽  
J. Sévely
Keyword(s):  
Carbon Fibers ◽  
Energy Analysis ◽  
Electron Excitation ◽  
Complex Structures ◽  
High Modulus ◽  
Promising Technique ◽  
X Ray ◽  
Fine Structures ◽  
X Ray Absorption

The present developments of electron energy analysis in the microscopes by E.E.L.S. allow an accurate recording of the spectra and of their different complex structures associated with the inner shell electron excitation by the incident electrons (1). Among these structures, the Extended Energy Loss Fine Structures (EXELFS) are of particular interest. They are equivalent to the well known EXAFS oscillations in X-ray absorption spectroscopy. Due to the EELS characteristic, the Fourier analysis of EXELFS oscillations appears as a promising technique for the characterization of composite materials, the major constituents of which are low Z elements. Using EXELFS, we have developed a microstructural study of carbon fibers. This analysis concerns the carbon K edge, which appears in the spectra at 285 eV. The purpose of the paper is to compare the local short range order, determined by this way in the case of Courtauld HTS and P100 ex-polyacrylonitrile carbon fibers, which are high tensile strength (HTS) and high modulus (HM) fibers respectively.

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