scholarly journals Reflexion and scattering of X-rays with change of frequency - II. Experimental

1942 ◽  
Vol 179 (978) ◽  
pp. 302-314 ◽  
Keyword(s):  
Quantum Theory ◽  
Low Temperatures ◽  
Diffuse Scattering ◽  
Absolute Intensity ◽  
Lattice Vibrations ◽  
X Rays ◽  
X Ray ◽  
Special Cases ◽  
Infra Red ◽  
Quantitative Explanation

It is shown that the quantum theory of X -ray reflexion and scattering in crystals developed in Part I is in full accord with the experimental facts. The theory succeeds in giving a quantitative explanation of the experimental facts concerning these phenomena as observed with diamond, viz. (1) the specular character of the quantum reflexion from the (111) planes, (2) the geometric law of such reflexion and especially the fact that, in general, the reflexion falls outside the plane of incidence, (3) the subsidiary features accompanying the reflexion, viz. faint elliptic spots and elongated streamers noticed in certain special cases, (4) the absolute intensity of the reflexion which is an appreciable fraction of the intensity of the classical reflexion, (5) the failure of the (110) planes to exhibit similar reflexions, (6) the persistence of the reflexions by the (111) planes with undiminished intensity at liquid air temperature and the relatively small increase of intensity at high temperatures, and (7) the appearance of a diffuse scattering having an undiminished intensity at low temperatures. The differences between diamond and other crystals in respect of these X -ray phenomena are explained by taking into consideration the differences in the frequency and character of their lattice vibrations in the infra-red region as revealed by the spectroscope.

scholarly journals On the ionization of light gases by X-rays. I.—Technique

1933 ◽  
Vol 141 (845) ◽  
pp. 669-686
Keyword(s):  
Absolute Intensity ◽  
X Rays ◽  
X Ray ◽  
Quantitative Correlation ◽  
Quantitative Measurements ◽  
Fluorescent Radiation ◽  
A New Technique ◽  
Heavy Gas ◽  
Reliable Correlation

The measurement of the intensity of an X-ray beam in absolute units is in theory most satisfactorily accomplished by a determination of its heating effect. The method, however, is attended by considerable experimental difficulties, so that its application is very limited, and in practice it is usual to replace it by a determination of the ionization produced when the beam is passed through a gas. To correlate the ionization with an absolute intensity requires a quantitative knowledge of the details of the interaction between the X-rays and the molecules concerned and of the ionization of the gas by the ejected electrons. It sometimes happens that the processes involved about which we know least are relatively unimportant, so that a fairly reliable correlation can be made; and much work has been done on the application of the ionization method to X-ray dosimetry. But in general a quantitative correlation between ionization and intensity is not possible. A further study of the ionization of gases by X-rays is therefore desirable; moreover it may be made to yield important information concerning the processes involved. The early development of the physics of X-rays contains many examples of this, and more recently an important contribution has been made by Stockmeyer. The events leading to the ionization of a heavy gas are exceedingly complicated, whereas in the light gases (hydrogen and helium) some of these events are absent or else occur to a negligible extent, so that the interpretation of experiments with the latter becomes simpler and more reliable. These gases are therefore specially worthy of study. Moreover, for them the application of quantum mechanics leads to the most definite results for comparison with experiment, and in particular permits of a direct test of some aspects of Dirac’s theory of recoil scattering. The ionization due to the gas itself is, however, very small, and may even be less than the secondary ionization due to electrons liberated from the chamber walls. The technique used in ionization measurements with heavy gases is therefore unsuitable. Hitherto the only attempt made to extend such measurements to light gases is an experiment carried out in 1915 on hydrogen by Shearer who, however, obtained very variable results and an ionization markedly smaller than that to be expected from recoil electrons alone. Moreover his experimental method is now open to criticism in view of our greater knowledge of X-rays, and in particular the fluorescent radiation used was of doubtful homogeneity. The present paper will describe a new technique suitable for quantitative measurements of the ionization produced by X-rays in light gases, and in another paper it will be applied to a re-investigation of hydrogen.

Diffuse scattering and phason modes in the i-AlPdMn quasicrystalline phase

2005 ◽  
Vol 220 (12) ◽  
Author(s):  
Marc de Boissieu ◽  
Sonia Francoual
Keyword(s):  
Elastic Constant ◽  
Elastic Constants ◽  
Intensity Distribution ◽  
Diffuse Scattering ◽  
Hydrodynamic Theory ◽  
Quasicrystalline Phase ◽  
X Rays ◽  
X Ray ◽  
Long Wavelength ◽  
Diffusive Modes

AbstractWe review results obtained in the study of the diffuse scattering in the i-AlPdMn quasicrystal. Most of the diffuse scattering is the result of long wavelength phason modes. The shape and intensity distribution of the diffuse scattering is well reproduced using the generalised elasticity theory and two phason elastic constants. The temperature dependence of the diffuse scattering indicates a softening of the phason elastic constant as the temperature is lowered. Using coherent X-rays and photo-correlation X-ray spectroscopy, it is shown that phason modes are collective diffusive modes, in agreement with the hydrodynamic theory of long wavelength fluctuations in quasicrystals.

X-Ray Diffuse Scattering Investigation of Defects in Ion Implanted and Annealed Silicon

1998 ◽  
Vol 524 ◽  
Author(s):  
C. H. Chang ◽  
U. Beck ◽  
T. H. Metzger ◽  
J. R. Patel
Keyword(s):  
Ion Implantation ◽  
Point Defect ◽  
Point Defects ◽  
Diffuse Scattering ◽  
Grazing Incidence ◽  
X Rays ◽  
Scattered Intensity ◽  
X Ray ◽  
Defect Clusters ◽  
Point Defect Clusters

ABSTRACTTo characterize the point defects and point defect clusters introduced by ion implantation and annealing, we have used grazing incidence x-rays to measure the diffuse scattering in the tails of Bragg peaks (Huang Scattering). An analysis of the diffuse scattered intensity will allow us to characterize the nature of point defects or defect clusters introduced by ion implantation. We have also observed unexpected satellite peaks in the diffuse scattered tails. Possible causes for the occurrence of the peaks will be discussed.

Theory of Detection of X-Rays by Superconductors

1997 ◽  
Vol 11 (19) ◽  
pp. 849-859 ◽  
Author(s):  
N. Murali Krishna ◽  
Lydia S. Lingam ◽  
Keshav N. Shrivastava
Keyword(s):  
Low Temperatures ◽  
Cooper Pair ◽  
Single Electron ◽  
Superconducting Film ◽  
Pair Breaking ◽  
X Rays ◽  
X Ray ◽  
Electron Process

Two new processes occur in a superconducting film when it is used as a detector of X-rays. One of these processes is the scattering of the X-ray by a single electron which gives rise to the broadening of the X-ray line. Another process describes the breaking of a Cooper pair by the X-ray which also contributes to the width of the X-ray. The line arising from the single electron process depends on T4 whereas that arising from the pair breaking process varies almost as T6 at low temperatures. Lines occur at ℏωq ± 2Δ, and at ℏωq where ℏωq is the energy of the X-ray and 2Δ is the gap of the superconductor.

Masquerade: removing non-sample scattering from integrated reflection intensities

2012 ◽  
Vol 45 (2) ◽  
pp. 292-298 ◽  
Author(s):  
J. A. Coome ◽  
A. E. Goeta ◽  
J. A. K. Howard ◽  
M. R. Probert
Keyword(s):  
Data Collection ◽  
Diffraction Data ◽  
Low Temperatures ◽  
Test Case ◽  
X Rays ◽  
Atmospheric Conditions ◽  
X Ray Diffraction ◽  
New Approach ◽  
X Ray ◽  
Internal Agreement

X-ray diffraction experiments at very low temperatures require samples to be isolated from atmospheric conditions and held under vacuum. These conditions are usually maintainedviathe use of beryllium chambers, which also scatter X-rays, causing unwanted contamination of the sample's diffraction pattern. The removal of this contamination requires novel data-collection and processing procedures to be employed. Herein a new approach is described, which utilizes the differences in origin of scattering vectors from the sample and the beryllium to eliminate non-sample scattering. The programMasqueradehas been written to remove contaminated regions of the diffraction data from the processing programs. Coupled with experiments at different detector distances, it allows for the acquisition of decontaminated data. Studies of several single crystals have shown that this approach increases data quality, highlighted by the improvement in internal agreement factor with the test case of cytidine presented herein.

X-Ray Diffuse Scattering from Cobalt Precipitates in Copper

1986 ◽  
Vol 82 ◽  
Author(s):  
B. C. Larson ◽  
S. Iida ◽  
J. Z. Tischler ◽  
J. D. Lewis ◽  
G. E. Ice ◽  
...  
Keyword(s):  
Crystal Lattice ◽  
Size Distribution ◽  
Diffuse Scattering ◽  
Large Angle ◽  
Host Lattice ◽  
Internal Strain ◽  
X Rays ◽  
X Ray ◽  
Scattering Measurements

ABSTRACTLarge-angle diffuse scattering has been investigated for the purpose of studying coherent precipitates in a crystal lattice. Detailed calculations have been made of the scattering near Bragg reflections from cobalt precipitates in a copper host lattice. These calculations have been compared to x-ray diffuse scattering measurements made on aged (570°C for 17 hr.) Cu-0.95%Co crystals with x-rays of three different wavelengths at the NSLS. The results indicate that the size distribution, the concentration, and the internal strain of the precipitates can be determined from such diffuse scattering measurements.

Optical and Dimensional Changes Which Accompany the Freezing and Melting of Hevea Rubber

1939 ◽  
Vol 12 (1) ◽  
pp. 18-30 ◽  
Author(s):  
W. Harold Smith ◽  
Charles Proffer Saylor
Keyword(s):  
Optical Properties ◽  
Low Temperatures ◽  
Heat Content ◽  
Uniaxial Crystal ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dimensional Changes ◽  
Ether Yield ◽  
The Individual

Abstract At suitable, low temperatures, unvulcanized rubber loses its elasticity and becomes hard and opaque. Similar changes frequently occur in baled rubber which has been tightly compressed before shipment. It is said to be frozen or “boardy.” The phenomenon has been studied by many investigators who have determined changes of volume, softening temperatures, the effects of increasing time of storage at low temperatures, the influence of pressure during freezing, and changes in heat capacity and entropy. These effects have generally been ascribed to a form of crystallization, and x-ray diffraction powder patterns indicate that crystals are present in frozen rubber. When total rubber is stretched, there are changes of volume and of heat content such as attend crystallization. With x-rays a crystal fiber pattern is obtained. It and the powder pattern obtained with frozen, compact rubber have been shown to indicate similar spacings and are assumed to be caused by the same type of crystal, the differences being ascribed to conditions of orientation. Dilute solutions of rubber hydrocarbon in ethyl ether yield small crystals of the hydrocarbon when they are subjected to temperatures between −35° and − 60° C. for several hours. The optical properties and melting points of these crystals and their x-ray diffraction patterns indicate their identity with the crystals in stretched and frozen rubber. Under the best conditions the crystals appear in spherulitic groupings, the individual needles in each spherulite having optical properties that closely approach those of a uniaxial crystal with negative elongation. The crystals of sol rubber which we obtained, melted between 9.5° and 11.0° C. Crystals of gel rubber melted between −2° and 14° C., but the melting ranges within this interval were not the same for all samples. Numerous observations have repeatedly confirmed the data. About 90 per cent of the rubber in solution may be obtained as birefringent material at −65° C. Temperatures between −40° and −50° C. have been preferred, however, because better crystals are obtained in that range.

scholarly journals Cosmic background X-rays produced by intergalactic innerbremsstrahlung

1970 ◽  
Vol 37 ◽  
pp. 372-373
Author(s):  
Satio Hayakawa
Keyword(s):  
Absolute Intensity ◽  
Proton Spectrum ◽  
X Rays ◽  
Background Component ◽  
Critical Test ◽  
X Ray ◽  
Cosmic Background ◽  
Distant Galaxies ◽  
Inverse Compton ◽  
The Absolute

It has been found difficult to explain both the absolute intensity and energy spectrum of the background component of cosmic X-rays in terms of a superposition of X-ray sources in distant galaxies [1] and of the inverse Compton collisions of metagalactic electrons with microwave photons [2]. Although the absolute intensity could be obtained by choosing suitable values of parameters which are not well known as yet, the gradual bending of the X-ray spectrum around 30 keV provides a critical test of theories. In this respect innerbremsstrahlung of intergalactic protons colliding with electrons is a candidate of background X-rays, since the X-ray spectrum is closely related to the proton spectrum and the latter usually bends in the non-relativistic region.

Adaptation of the X-Ray Diffraction Technique to the Analysis of Residual Stress in Carbo-Nitrided Steel Layers

2005 ◽  
Vol 490-491 ◽  
pp. 125-130
Author(s):  
Jean Michel Sprauel ◽  
H. Michaud
Keyword(s):  
Residual Stress ◽  
Carbon Content ◽  
Diffuse Scattering ◽  
Volume Fraction ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Quantitative Phase ◽  
Nitrided Steel ◽  
Stress Components

X-ray diffraction is used to analyse the fatigue behaviour of carbo-nitrided steel layers. Measurements are therefore carried out on the two major phases of the material, i.e. the martensite (a') and the retained austenite (g). On such gear material, X-ray residual stress evaluations are particularly difficult for three reasons. First, the studied material is multiphase. For that reason, in each phase, the stress component in the direction normal to the surface is non negligible. Second, the diffraction peaks obtained on the martensite are broadened, due to the overlap of different reflections of the tetragonal structure. Third, the material contains also carbide and nitride clusters, which lead to incoherent and diffuse scattering of X-rays thus making quantitative phase determination difficult. In our paper the methods used to solve these problems are presented. The development of a new quantitative phase analysis method which accounts for the variation of diffuse scattering of X-rays is shown first. The second part deals with an iterative micromechanical model implemented for the evaluation of the carbon content and the residual stress components of each phase. These methods are used for analysing the evolution with cycling fatigue of all the parameters derived from our enhanced analysis (phase volume fraction, carbon content, stress components, peak width).

scholarly journals Interface Evolution in a W/Si Multilayer after Rapid Thermal Annealing Studied by X-ray Reflectivity and Diffuse Scattering

1997 ◽  
Vol 30 (5) ◽  
pp. 642-646 ◽  
Author(s):  
M. Jergel ◽  
V. Holý ◽  
E. Majková ◽  
S. Luby ◽  
R. Senderák
Keyword(s):  
Thermal Annealing ◽  
Rapid Thermal Annealing ◽  
Diffuse Scattering ◽  
Grazing Incidence ◽  
Interface Roughness ◽  
X Rays ◽  
Interface Evolution ◽  
X Ray ◽  
Scattering Measurements ◽  
Highly Correlated

An interface study of the effect of rapid thermal annealing (RTA) in the temperature range 523–1273 K for 5–40 s on a nominally [(50 Å Si/10 Å W) × 9] amorphous multilayer (ML) deposited on an Si(100) wafer was performed by X-ray reflectivity and diffuse-scattering measurements at grazing incidence. The results of the X-ray reflectivity and diffuse-scattering measurements were evaluated by Fresnel optical computational code and within the distorted-wave Born approximation, respectively. Up to the 773 K/5 s annealing step, the r.m.s. interface roughness decreases by 30%, which brings about a reflectivity increase of 20% on the first Bragg maximum. There is a small overall increase of the r.m.s. interface roughness across the ML in the as-deposited state and the interface profiles are highly correlated. From the very beginning of RTA, the fractal interface behaviour is gradually lost and the lateral correlation length increases, this process being accompanied by a decrease of the interface conformality. This tendency continues during the 773 K/20 s annealing; however, the r.m.s. roughness evolution is reversed. During the 1023 K/5 s annealing, the interfaces are no longer `seen' by the X-rays and, during the 1273 K/5 s annealing, a total collapse of the ML structure takes place.

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