scholarly journals VUV and Soft X-ray Spectroscopy of Actinides

2003 ◽  
Vol 802 ◽  
Author(s):  
Clifford G. Olson ◽  
John J. Joyce ◽  
Tomasz Durakiewicz ◽  
Elzbieta Guziewicz ◽  
Martin Butterfield
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Spectral Characteristics ◽  
Electronic States ◽  
Momentum Dependence ◽  
Auger Electrons ◽  
X Ray ◽  
Relative Cross Section ◽  
Initial States ◽  
Valence Bands

ABSTRACTOptical and photoelectron spectroscopies using VUV and Soft X-ray photons are powerful tools for studies of elemental and compound actinides. Large changes in the relative atomic cross sections of the 5f, 6d and sp electrons allow decomposition of the character of the valence bands using photoemission. Resonant enhancement of photoelectrons and Auger electrons at the 5d core threshold further aids the decomposition and gives a measure of elemental specificity. Angle-resolved photoemission can be used to map the momentum dependence of the electronic states. The large changes in relative cross section with photon energy yields further details when the mapping is done at equivalent points in multiple zones. Spectra for well understood rare earth materials will be presented to establish spectral characteristics for known atomic character initial states. These signatures will be applied to the case of USb to investigate f-d hybridization near the Fermi level.

Cross-Sections for K-Shell Excitation by Fast Electrons

1977 ◽  
Vol 35 ◽  
pp. 252-253
Author(s):  
R. F. Egerton ◽  
D. C. Joy
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Unit Volume ◽  
Direct Method ◽  
Specimen Thickness ◽  
Thin Specimen ◽  
Auger Electrons ◽  
Fast Electrons ◽  
X Ray ◽  
Image Position

The cross-section for excitation of an electron from the innermost shell of a given atom can be determined directly by measuring the proportion of fast incident electrons which have suffered an appropriate energy loss, or (if the X-ray or Auger yields are known) from the number of X-ray quanta or Auger electrons emitted as a result of de-excitation.In the direct method, this cross-section is obtained as a function of α, the maximum scattering angle allowed into the detector, and for a thin specimen it is given by:where n is the number of atoms per unit volume of specimen, t is the specimen thickness, Ik(α) represents the number of K-loss electrons reaching the detector and It represents the total number of fast electrons entering the detector,1 for the same value of α. Equation (1) can also be used12 for microanalysis of low-atomic-number elements in order to measure n or nt if σK(α) is known.

scholarly journals Atomic cross-section effects in soft-x-ray photoemission from Ag valence bands

1976 ◽  
Vol 14 (6) ◽  
pp. 2411-2416 ◽  
Author(s):  
P. S. Wehner ◽  
J. Stöhr ◽  
G. Apai ◽  
F. R. McFeely ◽  
R. S. Williams ◽  
...  
Keyword(s):  
Cross Section ◽  
X Ray ◽  
Valence Bands

Electronic states of core levels and valence bands for KxC60 studied by X-ray photoelectron spectroscopy

1991 ◽  
Vol 181 (4-6) ◽  
pp. 320-324 ◽  
Author(s):  
Y. Fukuda ◽  
N. Sanada ◽  
M. Nagoshi ◽  
T. Takahashi ◽  
H. Katayama-Yoshida ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Electronic States ◽  
X Ray ◽  
Valence Bands

scholarly journals Pore shape and sorption behaviour in mesoporous ordered silica films

2016 ◽  
Vol 49 (5) ◽  
pp. 1713-1720 ◽  
Author(s):  
Gerhard Fritz-Popovski ◽  
Roland Morak ◽  
Parvin Sharifi ◽  
Heinz Amenitsch ◽  
Oskar Paris
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Grazing Incidence ◽  
Dip Coating ◽  
Silica Films ◽  
Elliptical Cross ◽  
Sorption Behaviour ◽  
X Ray ◽  
Pluronic P123 ◽  
X Ray Scattering

Mesoporous silica films templated by pluronic P123 were prepared using spin and dip coating. The ordered cylindrical structure within the films deforms due to shrinkage during calcination. Grazing-incidence small-angle X-ray scattering (GISAXS) measurements reveal that both the unit cell and the cross section of the pores decrease in size, mainly normal to the surface of the substrate, leading to elliptical cross sections of the pores with axis ratios of about 1:2. Water take-up by the pores upon changing the relative humidity can be monitored quantitatively by the shift in the critical angle of X-ray reflection as seen by the Yoneda peak.

scholarly journals Coherent neutrino scattering off the 48Ti nucleus

2012 ◽  
Vol 20 ◽  
pp. 104
Author(s):  
D. K. Papoulias ◽  
T. S. Kosmas
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Energy Region ◽  
Decomposition Method ◽  
Form Factors ◽  
Momentum Dependence ◽  
Neutrino Scattering ◽  
Neutrino Detection ◽  
Supernova Neutrino ◽  
Coherent Neutrino Scattering

The method of fractional occupation probabilities of the orbits is adopted in order to obtain nuclear form factors to be used for reliable cross sections calculations of the dominant coherent neutrino-nucleus reaction channel. To this purpose, the multipole decomposition method of Donnelly-Walecka is employed. The response of the 48Ti nucleus in solar and Supernova neutrino detection is investigated through our realistic nuclear structure cross sections calculations, based on the solution of the BCS equations. The present results indicate that the momentum dependence of the nuclear form factors cannot be neglected from the cross section, especially in the energy region of Supernova neutrinos (or for neutrinos having higher energies), because differences of even orders of magnitude may occur.

FiXR: a framework to reconstruct fiber cross-sections from X-ray fiber diffraction experiments

2020 ◽  
Vol 76 (2) ◽  
pp. 102-117
Author(s):  
Biel Roig-Solvas ◽  
Dana H. Brooks ◽  
Lee Makowski
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Amyloid Β ◽  
Diffraction Theory ◽  
Saxs Data ◽  
Molecular Conformations ◽  
X Ray ◽  
X Ray Scattering ◽  
Reconstruction Methods ◽  
Optimization Heuristics

Ab initio reconstruction methods have revolutionized the capabilities of small-angle X-ray scattering (SAXS), allowing the data-driven discovery of previously unknown molecular conformations, exploiting optimization heuristics and assumptions behind the composition of globular molecules. While these methods have been successful for the analysis of small particles, their impact on fibrillar assemblies has been more limited. The micrometre-range size of these assemblies and the complex interaction of their periodicities in their scattering profiles indicate that the discovery of fibril structures from SAXS measurements requires novel approaches beyond extending existing tools for molecular discovery. In this work, it is proposed to use SAXS measurements, together with diffraction theory, to infer the electron distribution of the average cross-section of a fiber. This cross-section is modeled as a discrete electron density with continuous support, allowing representations beyond binary distributions. Additional constraints, such as non-negativity or smoothness/connectedness, can also be added to the framework. The proposed approach is tested using simulated SAXS data from amyloid β fibril models and using measured data of Tobacco mosaic virus from SAXS experiments, recovering the geometry and density of the cross-sections in all cases. The approach is further tested by analyzing SAXS data from different amyloid β fibril assemblies, with results that are in agreement with previously proposed models from cryo-EM measurements. The limitations of the proposed method, together with an analysis of the robustness of the method and the combination with different experimental sources, are also discussed.

scholarly journals Hadron wave functions in high-energy scattering, form factors and strong decays: The effects of the Lorentz contracted form

2021 ◽  
Vol 36 (37) ◽  
Author(s):  
Yu. A. Simonov
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Lorentz Invariance ◽  
Form Factors ◽  
High Energy ◽  
Wave Functions ◽  
Large Momentum ◽  
Momentum Dependence ◽  
Lorentz Contraction ◽  
Energy Hadron

In this paper, we study the class of the processes, where dynamics depends essentially on the properties of the hadron wave functions involved in the reactions. In this case, the momentum dependence of the form of the wave functions, imposed by the Lorentz invariance and in particular by the Lorentz contraction, can be tested in the experiment and may strongly influence the resulting cross-sections. One example of such observables is given by the hadron form factors in the case when the large [Formula: see text] behavior is mostly frozen, while the Lorentz contraction of the hadron wave functions is taken into account. Another example, considered earlier, is the strong hadron decay with high-energy emission. In this paper, we study the role of the Lorentz contraction in the high-energy hadron–hadron scattering process at large momentum transfer. For the [Formula: see text] and [Formula: see text] scattering at large [Formula: see text], it is shown that at small [Formula: see text], the picture of two exponential slopes in the differential cross-section, explained previously by the author, remains stable, while the backward scattering cross-section is strongly increased by the Lorentz contraction.

Determination of K shell absorption parameters for some lanthanides using the X-ray attenuation method

2015 ◽  
Vol 93 (12) ◽  
pp. 1532-1540 ◽  
Author(s):  
F. Akman ◽  
R. Durak ◽  
M.R. Kaçal
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Experimental Results ◽  
Secondary Source ◽  
X Rays ◽  
Strength Parameters ◽  
X Ray ◽  
Total Attenuation ◽  
First Time

The total attenuation cross section at the K edge, absorption jump ratio, jump factor, Davisson–Kirchner ratio, and oscillator strength parameters for the K shell were determined by measuring the total attenuation cross sections around the K edge for Pr, Nd2O3, and Sm. The measurements were performed in a secondary excitation geometry using the Kα2, Kα1, Kβ1, and Kβ2 X-rays (in the region from 31.817 to 55.293 keV) from different secondary source targets excited by the 59.54 keV γ-photons from an 241Am annular source. It is the first time that the Davisson–Kirchner ratio values have been determined for present samples. The experimental results were compared with the theoretically calculated and other available experimental results.

Neural network prediction of K and L-shell X-ray production cross sections

2018 ◽  
Vol 106 (12) ◽  
pp. 1017-1021
Author(s):  
Brahim Beladel ◽  
Brahim Mohamedi ◽  
Abdelkader Guesmia ◽  
Mohamed E. A. Benamar
Keyword(s):  
Neural Network ◽  
Cross Section ◽  
Cross Sections ◽  
Production Cross ◽  
Alpha Particles ◽  
X Ray ◽  
Fundamental Parameters ◽  
The Neural Network ◽  
Neural Network Prediction ◽  
Network Prediction

Abstract The ionization and X-ray production cross section are fundamental parameters in elemental analysis by PIXE technique. Unfortunately no exact general analytical expression exists, from which the interest of this work. In this paper, we apply the neural network technique in the evaluation of the X-ray production cross sections. The calculations are based on Mukoyama’s PWBA data. Our results are compared with experimental data for protons and alpha particles for energies ranging from hundreds KeV to tens MeV.

Angular variations of K and L X-ray fluorescence cross sections for some lanthanides

2008 ◽  
Vol 86 (2) ◽  
pp. 361-367 ◽  
Author(s):  
I Han ◽  
M Şahin ◽  
L Demir
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Emission Angle ◽  
X Rays ◽  
X Ray ◽  
Isotropic Distribution ◽  
Fluorescence Cross Section ◽  
Intensity Ratios ◽  
Experimental Values ◽  
Photon Source

Kα, Kβ, Lα, and Lβ X-ray fluorescence cross sections for lanthanides in the atomic range 62 ≤ Z ≤ 68 (Sm, Eu, Gd Tb, Dy, Ho, and Er) were simultaneously measured by 59.54 keV incident photon energy at five angles ranging from 120° to 160°. The measurements were performed using an Am-241 radioisotope as the photon source and a Si(Li) detector. The Lα X-ray fluorescence cross section (σLα) was found to decrease with increasing emission angle and showed an anisotropic distribution of Lα X-rays. Kα, Kβ, and Lβ X-ray fluorescence cross sections (σKα, σKβ, and σLβ) were observed to be angle-independent and showed an isotropic distribution of Kα, Kβ, and Lβ X-rays. The Kα and Kβ X-rays originate from filling of the K shell (J = 1/2) vacancies, Lβ X-rays from filling of the L1 and L2 (J = 1/2) subshell vacancies, and Lα X-rays from filling of the L3 subshell (J = 3/2) vacancy. The fluorescent X-rays originating from the vacancy states with J = 1/2 are isotropic and unpolarized, but fluorescent X-rays originating from the vacancy states with J > 1/2 are anisotropic and polarized. Thus, the atomic inner shells vacancy states with J > 1/2 are aligned whereas vacancy states with J = 1/2 are not aligned. Lα fluorescence X-rays have an anisotropic distribution, while Kα, Kβ, and Lβ fluorescence X-rays have isotropic distribution. Furthermore, the IKβ/IKα, ILα/IKα}, ILβ/IKα, and ILβ/ILα intensity ratios for the elements under investigation were determined. The experimental cross sections and intensity ratios for Kα, Kβ, Lα, and Lβ fluorescence X-rays were also determined, and these experimental values were compared with our calculated theoretical values.PACS Nos.: 32.30.Rj, 32.80.Cy

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