The Phase of Scattering Profiles & X-Ray/Neutron Reflectivity

1994 ◽  
Vol 376 ◽  
Author(s):  
P.S. Pershan
Keyword(s):  
Critical Angle ◽  
Scattering Amplitude ◽  
Surface Scattering ◽  
Neutron Reflectivity ◽  
Phase Problem ◽  
X Ray Diffraction ◽  
Phase Information ◽  
X Ray ◽  
Reflectivity Data ◽  
Amplitude Density

ABSTRACTThe phase problem that troubles x-ray diffraction is also a problem for x-ray and neutron reflectivity; however, there are a range of small angles just beyond the critical angle for which the reflectivity contains information on the phase of the surface scattering amplitude. In principle this phase information can be used to determine the asymmetry of the normal gradient of the scattering amplitude density. We discuss here practical conditions under which this symmetry can, or cannot, be extracted from reflectivity data.

Structural Properties Of Co/Re Superlattices

1991 ◽  
Vol 238 ◽  
Author(s):  
Y. Huai ◽  
R. W. Cochrane ◽  
Y. Shi ◽  
H. E. Fischer ◽  
M. Sutton
Keyword(s):  
Structural Disorder ◽  
Multilayer Films ◽  
Film Plane ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bilayer Films ◽  
Out Of Plane ◽  
Reflectivity Data ◽  
Sharp Interfaces ◽  
Good Agreement

ABSTRACTThe structures of equal-thickness Co/Re multilayer films and several Co/Re bilayer films have been investigated by X-ray diffraction at low and high angles. Analysis of low-angle reflectivity data from bilayer films indicates that interfacial intermixing is limited to three monolayers and that the two interfacial configurations are different. The high-angle X-ray diffraction data show that multilayer films have coherent interfaces and a highly textured structure with hep [002] orientations normal to the film plane for periods 21 Å ≤ Λ ≤220 Å. Detailed structures have been determined by fitting the X-ray spectra to calculated ones using a trapezoidal model. The results indicate that samples with 42 Å≤ Λ ≤220 Å have relatively sharp interfaces, in good agreement with the bilayer results. In addition, an out-of-plane expansion of the Co (002) layer is observed in samples with large Λ and results from structural disorder leading to a reduced atomic density. For Λ <21 Å the interfaces arise from the rougher surfaces of the deposited layers.

scholarly journals The Use of Connected Masks for Reconstructing the Single Particle Image from X-Ray Diffraction Data. II. The Dependence of the Accuracy of the Solution on the Sampling Step of Experimental Data

2015 ◽  
Vol 10 (2) ◽  
pp. 508-525 ◽  
Author(s):  
Н.Л. Лунина ◽  
N.L. Lunina
Keyword(s):  
Experimental Data ◽  
Particle Image ◽  
Expected Improvement ◽  
Problem Solution ◽  
Phase Problem ◽  
X Ray Diffraction ◽  
Sampling Step ◽  
X Ray ◽  
X Ray Crystallography ◽  
Grid Points

Advances in the methodology of the X-ray diffraction experiments leads to a possibility to register the rays scattered by large isolated biological particles (viruses and individual cells) but not only by crystalline samples. The experiment with an isolated particle provides researchers with the intensities of the scattered rays for the continuous spectrum of scattering vectors. Such experiment gives much more experimental data than an experiment with a crystalline sample where the information is limited to a set of Bragg reflections. This opens up additional opportunities in solving underlying problem of X-ray crystallography, namely, calculating phase values for the scattered waves needed to restore the structure of the object under study. In practice, the original continuous diffraction pattern is sampled, reduced to the values at grid points in the space of scattering vectors (in the reciprocal space). The sampling step determines the amount of the information involved in solving the phase problem and the complexity of the necessary calculations. In this paper, we investigate the effect of the sampling step on the accuracy of the phase problem solution obtained by the method proposed earlier by the authors. It is shown that an expected improvement of the accuracy of the solution with the reducing the sampling step continues even after crossing the Nyquist limit defined as the inverse of the double size of the object under study.

Surface structure analysis of Si(111)−Bi by X-ray diffraction — Approach to the solution of the phase problem

1987 ◽  
Vol 191 (3) ◽  
pp. L825-L834 ◽  
Author(s):  
Toshio Takahashi ◽  
Shinichiro Nakatani ◽  
Tetsuya Ishikawa ◽  
Seishi Kikuta
Keyword(s):  
Surface Structure ◽  
Structure Analysis ◽  
Phase Problem ◽  
X Ray Diffraction ◽  
X Ray

Model-independent inversion of x-ray or neutron reflectivity data

2001 ◽  
Vol 63 (19) ◽  
Author(s):  
Erman Bengu ◽  
Monica Salud ◽  
L. D. Marks
Keyword(s):  
Neutron Reflectivity ◽  
X Ray ◽  
Model Independent ◽  
Reflectivity Data

Structural characterization of sputter-deposited LaNiO3 thin films on Si substrate by x-ray reflectivity and diffraction

1997 ◽  
Vol 12 (11) ◽  
pp. 3165-3173 ◽  
Author(s):  
Hsin-Yi Lee ◽  
Tai-Bor Wu
Keyword(s):  
Thin Films ◽  
Transition Layer ◽  
Mass Density ◽  
Composition Analysis ◽  
X Ray Diffraction ◽  
Diffraction Intensity ◽  
Si Substrate ◽  
X Ray ◽  
Sputter Deposited ◽  
Reflectivity Data

X-ray reflectivity and diffraction were applied to characterize the highly (100)-textured thin films of LaNiO3, which were deposited on Si substrate via radio frequency magnetron sputtering at temperatures ranging from 250 to 450 °C. Two interference fringes of different period were observed from the reflectivity curves, and the fitting result indicates that in addition to the normal lanthanum-nickel oxide layer, a transition layer, which has a larger mass density than the previous one, exists in the sputter-deposited films. A comparison of the measured x-ray diffraction intensity with that calculated from layer thickness and mass density obtained from reflectivity data indicates that the transition layer is noncrystalline. The x-ray diffraction result also shows that there is a significant decrease of (100) diffraction intensity relative to that of (200) as increasing the deposition temperature. Using the reflectivity and diffraction data along with results of electron diffraction and film composition analysis from our other studies, such a change of relative intensity between the two diffraction peaks is attributed to the increasing content of two also highly textured La-rich phases, i.e., (110)-textured La4Ni3O10 and (100)-textured La2NiO4, in addition to the LaNiO3.

The information available from anomalous scattering on fibres at different wavelengths

1987 ◽  
Vol 20 (4) ◽  
pp. 295-299 ◽  
Author(s):  
C. Nave
Keyword(s):  
Absorption Edge ◽  
Heavy Atom ◽  
Imaginary Component ◽  
Anomalous Scattering ◽  
Phase Problem ◽  
Phase Information ◽  
Helical Symmetry ◽  
X Ray ◽  
The Real ◽  
X Ray Scattering

The contribution of a particular atom in a molecule to the total X-ray scattering can be altered by varying the wavelength in the region of the absorption edge of the atom. It is shown that only the changes in the real part of the anomalous scattering of the atom provide significant changes in a pattern from a fibre containing molecules with helical symmetry. Changes due to the imaginary component are small and Friedel differences cannot be observed, owing to the fibre disorder. The information which can be obtained is equivalent to that given by a truly isomorphous heavy-atom derivative. For the general case this is not sufficient to provide unambiguous phase information. If a twofold axis is present at right angles to the fibre axis then the amplitudes are real and the phase problem can, in favourable cases, be solved.

scholarly journals Solution to the phase problem for surface X-ray diffraction

2008 ◽  
Vol 64 (a1) ◽  
pp. C109-C109
Author(s):  
P.F. Lyman ◽  
V.L. Shneerson ◽  
R. Fung ◽  
R.J. Harder ◽  
S.S. Parihar ◽  
...  
Keyword(s):  
Phase Problem ◽  
X Ray Diffraction ◽  
X Ray
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