Influence of multiple scattering of relativistic electrons on the linewidth of Parametric X-ray Radiation produced in the extremely Bragg geometry in the absence of photoabsorption

2016 ◽  
Vol 127 ◽  
pp. 7-12 ◽  
Author(s):  
Mehdi Tabrizi
Keyword(s):  
Multiple Scattering ◽  
Relativistic Electrons ◽  
X Ray ◽  
Bragg Geometry

Coherent X-Rays Generated by Relativistic Electrons in a Tungsten Monocrystal

2015 ◽  
Vol 1084 ◽  
pp. 217-220
Author(s):  
Yuri Adischev ◽  
Victor Zabaev ◽  
Valery Kaplin ◽  
Sergey Kuznetsov ◽  
Sergey Uglov ◽  
...  
Keyword(s):  
Electron Beam ◽  
Bragg Angle ◽  
Angular Distributions ◽  
Relativistic Electrons ◽  
X Rays ◽  
Photon Yield ◽  
X Ray ◽  
Bragg Geometry

In an experiment conducted at the Tomsk synchrotron "Sirius", the photon yield of parametric X-ray radiation generated by 500 MeV electrons in a tungsten monocrystal in Bragg geometry has been studied. The (111) tungsten monocrystal, having a thickness of 1.7 mm and a surface mosaicity of not more than 80², was oriented at the Bragg angle θB= 45°to the direction of the electron beam. The photons were detected at the angle 2θB= 90° relative to the electron beam. A comparison of PXR angular distributions with calculations has been carried out with taking into account the actual conditions of the experiment.

Investigation of the phase shift in X-ray forward diffraction using an X-ray interferometer

1998 ◽  
Vol 5 (3) ◽  
pp. 967-968 ◽  
Author(s):  
Keiichi Hirano ◽  
Atsushi Momose
Keyword(s):  
Phase Shift ◽  
Silicon Crystal ◽  
Dynamical Theory ◽  
Perfect Crystal ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bragg Geometry

The phase shift of forward-diffracted X-rays by a perfect crystal is discussed on the basis of the dynamical theory of X-ray diffraction. By means of a triple Laue-case X-ray interferometer, the phase shift of forward-diffracted X-rays by a silicon crystal in the Bragg geometry was investigated.

Extended X-ray absorption fine structure and multiple-scattering simulation of nickel dithiolene complexes Ni[S2C2(CF3)2]2n(n= −2, −1, 0) and an olefin adduct Ni[S2C2(CF3)2]2(1-hexene)

2015 ◽  
Vol 22 (1) ◽  
pp. 124-129 ◽  
Author(s):  
Weiwei Gu ◽  
Hongxin Wang ◽  
Kun Wang
Keyword(s):  
Fine Structure ◽  
Multiple Scattering ◽  
Edge Structure ◽  
X Ray ◽  
Absorption Fine ◽  
Square Planar ◽  
Square Planar Complexes ◽  
Uv Visible ◽  
Edge Features ◽  
X Ray Absorption

A series of Ni dithiolene complexes Ni[S2C2(CF3)]2n(n= −2, −1, 0) (1,2,3) and a 1-hexene adduct Ni[S2C2(CF3)2]2(C6H12) (4) have been examined by NiK-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine-structure (EXAFS) spectroscopies. Ni XANES for1–3reveals clear pre-edge features and approximately +0.7 eV shift in the NiK-edge position for `one-electron' oxidation. EXAFS simulation shows that the Ni—S bond distances for1,2and3(2.11–2.16 Å) are within the typical values for square planar complexes and decrease by ∼0.022 Å for each `one-electron' oxidation. The changes in NiK-edge energy positions and Ni—S distances are consistent with the `non-innocent' character of the dithiolene ligand. The Ni—C interactions at ∼3.0 Å are analyzed and the multiple-scattering parameters are also determined, leading to a better simulation for the overall EXAFS spectra. The 1-hexene adduct4presents no pre-edge feature, and its NiK-edge position shifts by −0.8 eV in comparison with its starting dithiolene complex3. Consistently, EXAFS also showed that the Ni—S distances in4elongate by ∼0.046 Å in comparison with3. The evidence confirms that the neutral complex is `reduced' upon addition of olefin, presumably by olefin donating the π-electron density to the LUMO of3as suggested by UV/visible spectroscopy in the literature.

A Combination Method of Charge Density Measurement in Hard Materials Using Accurate, Quantitative Electron and X-ray Diffraction: The α-Al2O3 Case

2003 ◽  
Vol 9 (5) ◽  
pp. 419-427 ◽  
Author(s):  
Victor A. Streltsov ◽  
Philip N.H. Nakashima ◽  
Andrew W.S. Johnson
Keyword(s):  
Charge Density ◽  
Multiple Scattering ◽  
Density Measurement ◽  
Bloch Wave ◽  
Combination Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hard Materials ◽  
Structure Factors ◽  
Free Data

Current X-ray diffraction techniques intended for “ideally imperfect” specimens provide structure factors only on a relative scale and ever-present multiple scattering in strong low-angle Bragg reflections is difficult to correct. Multiple scattering is implicit in the quantitative convergent beam electron diffraction (QCBED) method, which provides absolutely scaled structure factors. Conventional single crystal X-ray diffraction has proved adequate in softer materials where crystal perfection is limited. In hard materials, the highly perfect nature of the crystals is often a difficulty, due to the inadequacy of the conventional corrections for multiple scattering (extinction corrections). The present study on α-Al2O3 exploits the complementarity of synchrotron X-ray measurements for weak and medium intensities and QCBED measurement of the strong low-angle reflections. Two-dimensional near zone axis QCBED data from different crystals at various accelerating voltages, thicknesses, and orientations have been matched using Bloch-wave and multislice methods. The reproducibility of QCBED data is better than 0.5%. The low-angle strong QCBED structure factors were combined with middle and high-angle extinction-free data from synchrotron X-ray diffraction measurements. Static deformation charge density maps for α-Al2O3 have been calculated from a multipole expansion model refined using the combined QCBED and X-ray data.

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