scholarly journals The reflection of X-rays from anthracene crystals

1933 ◽  
Vol 142 (847) ◽  
pp. 422-447 ◽  
Keyword(s):  
Relative Intensity ◽  
X Rays ◽  
Ray Method ◽  
X Ray ◽  
Intensity Measurements ◽  
X Ray Scattering ◽  
Inorganic Substances ◽  
The Absolute ◽  
Absolute Measurements

The importance of absolute, as opposed to relative, intensity measurements in X-ray crystal analysis has often been stressed, and such measurements may lead, with compounds where one sort of atom is of dominant importance, to a direct and unequivocal determination of the structure. Their value in the analysis of organic compounds, where usually no atoms are predominant in X-ray scattering power, is perhaps not so immediate; nevertheless, the absolute X-ray reflection of a given substance is at least as important a constant as, say, its thermal conductivity, and its determination is a necessary preliminary to any detailed study by the X-ray method. Hitherto such absolute measurements have been confined to inorganic substances e. g. , rock-salt, usually occurring in large crystals. It seemed to be worth while to make a determination of the absolute reflecting power of a typical organic crystal in conditions similar to those employed in the analysis of such crystals, i. e. , using a small crystal completely bathed in a monochromatic pencil of X-rays. A very suitable substance for such a measurement is anthracene , since it is easily obtained pure and in crystals which are reasonably permanent and simple to adjust, but more particularly because its structure is already known in considerable detain and relative intensity measurements described in this paper will enable workers with other crystals to standardize series of relative intensity measurements with the minimum of labour, by comparing directly one of their observed reflections with the (001) reflection from a small weighed crystal of anthracene. The comparison can be made without difficulty, either photographically using an integrating microphotometer or by the ionization method on an ordinary spectrometer.

X-Ray Determination of Site Occupation Parameters in Ordered Ternaries Cu(Aux.M1x.)M = Ni,Pd

1990 ◽  
Vol 213 ◽  
Author(s):  
R. Kumar ◽  
C. J. Sparks ◽  
T. Shiraishi ◽  
E.D. Specht ◽  
P. Zschack ◽  
...  
Keyword(s):  
Rietveld Method ◽  
Scattering Data ◽  
X Rays ◽  
X Ray ◽  
Site Occupation ◽  
Intensity Measurements ◽  
X Ray Scattering ◽  
Chemical Phase ◽  
Multiple Wavelengths ◽  
Scattering Factor

ABSTRACTX-ray scattering data obtained for multiple wavelengths with synchrotron radiation were analyzed by the Rietveld method to determine Ni and Pd distributions on the Cu(000) and Au(½½½) sites in the CuAuI tetragonal P4/mmm structure. Alloys of CuAuxM1-x containing 6 at. % Ni or 10 and 25 at. % Pd were processed to obtain maximum ordering. Nickel is predominantly found on the Cu site and most all the Pd is found on the Au site. The uncertainty in site occupation parameters is discussed for various contributions which affect powder intensity measurements. For highly absorbing materials, an observed powder roughness effect decreases the low angle (2θ) intensities relative to the high 2θ intensities. This effect reduces the reliability of the thermal parameters and obscures a proper description of the thermal motion of the two sublattices. Corrections to the X-ray intensity data for surface roughness/porosity effects reduce uncertainties to about ±1 at. % on the refined value of the site occupations. This use of variable wavelength X-rays with simultaneous refinement of the corresponding data is capable of distinguishing site occupations even between two elements of almost equal scattering factor as, for example, Cu and Ni atoms in this investigation. Chemical phase stability is related to the site occupation parameters.

Quantitative Determination of Carbon in Solid Hydrocarbons Using the Intensity Ratio of Incoherent to Coherent Scattering of X-Rays

1964 ◽  
Vol 18 (6) ◽  
pp. 171-174 ◽  
Author(s):  
C. J. Toussaint ◽  
G. Vos
Keyword(s):  
Intensity Ratio ◽  
Coherent Scattering ◽  
X Rays ◽  
Ray Method ◽  
Sample Weight ◽  
X Ray ◽  
Carbon Determination ◽  
Solid Hydrocarbons ◽  
Good Agreement

A method is presented for the determination of carbon in solid hydrocarbons using the intensity ratio of incoherent to coherent scattering of x-rays. The method is very rapid with precision at the 95% confidence level of about ±0.3%. The minimum sample weight necessary is 0 2 g. Analysis of samples by the x-ray method shows good agreement with values obtained by microcombustion. Finally a general comparison between different methods for carbon determination in solid hydrocarbons is discussed.

Apparatus for the simultaneous measurement of the X-ray absorption factor developed for a small-angle X-ray scattering beamline

2007 ◽  
Vol 40 (4) ◽  
pp. 791-795 ◽  
Author(s):  
Takeshi Morita ◽  
Yoshitada Tanaka ◽  
Kazuki Ito ◽  
Yoshihiro Takahashi ◽  
Keiko Nishikawa
Keyword(s):  
Small Angle ◽  
Performance Test ◽  
X Rays ◽  
Absorption Factor ◽  
X Ray ◽  
X Ray Scattering ◽  
X Ray Absorption ◽  
Scattering Measurement ◽  
Ray Scattering

A novel apparatus has been developed that enables the simultaneous determination of the absorption factor during measurement of small-angle X-ray scattering (SAXS) intensities of a sample. It was designed especially for the use of relatively low-energy X-rays at SAXS beamlines of synchrotron facilities. The X-ray intensity of transmittance is measured by a silicon PIN photodiode, which is implanted in a direct beamstop set in a vacuum chamber. Since the assembly transmits an attenuated direct beam to a detector during the scattering measurement, a zero-angle position can be monitored without additional operation. It was confirmed that the linearity between the signal from the photodiode and the intensity of X-rays is good and the photodiode is applicable for the desired purpose. For a performance test, the absorption factors of a supercritical fluid were measured with a wide density range.

FEATURES OF X-RAY ANALYSIS OF CRYSTALLINITY DEGREE OF POLYPROPYLENE FIBRES

2018 ◽  
Vol 59 (7) ◽  
pp. 80 ◽  
Author(s):  
Aleksandr Ye. Zavadskii
Keyword(s):  
Degree Of Crystallinity ◽  
X Rays ◽  
Ray Method ◽  
Polypropylene Fibres ◽  
Crystallinity Degree ◽  
X Ray ◽  
Diffuse Halo ◽  
Standard Powder ◽  
Polymer Crystallinity

The need to take into account the anisotropy of compact samples pressed from grinded polypropylene (PP) fibres at a determination of the degree of polymer crystallinity by X-ray method was shown. It was proved that the breach of the spherical scattering symmetry of X-rays by PP fiber samples is not connected with an amorphous phase of polymer. The method for calculating the degree of crystallinity of fibres from the normalized intensity of the diffuse halo of preparations under study and standard powder PP samples was proposed.

Bragg–von Laue diffraction generalized to twisted X-rays

2016 ◽  
Vol 72 (2) ◽  
pp. 190-196 ◽  
Author(s):  
Dominik Jüstel ◽  
Gero Friesecke ◽  
Richard D. James
Keyword(s):  
Plane Waves ◽  
Atomic Scale ◽  
Periodic Case ◽  
X Rays ◽  
Helical Structures ◽  
Ray Method ◽  
X Ray ◽  
Closed Form Solutions ◽  
Ray Methods

A pervasive limitation of nearly all practical X-ray methods for the determination of the atomic scale structure of matter is the need to crystallize the molecule, compound or alloy in a sufficiently large (∼10 × 10 × 10 µm) periodic array. In this paper an X-ray method applicable to structure determination of some important noncrystalline structures is proposed. It is designed according to a strict mathematical analog of von Laue's method, but replacing the translation group by another symmetry group, and simultaneously replacing plane waves by different exact closed-form solutions of Maxwell's equations. Details are presented for helical structures like carbon nanotubes or filamentous viruses. In computer simulations the accuracy of the determination of structure is shown to be comparable to the periodic case.

scholarly journals The crystalline structure of anthracene. A quantitative X-ray investigation

1933 ◽  
Vol 140 (840) ◽  
pp. 79-98 ◽  
Keyword(s):  
Organic Compounds ◽  
Aromatic Hydrocarbons ◽  
Magnetic Measurements ◽  
Upright Position ◽  
Ray Method ◽  
Tetrahedral Structure ◽  
X Ray ◽  
Intensity Measurements ◽  
Graphite Structure ◽  
Absolute Measurements

The aromatic hydrocarbons naphthalene and anthracene were among the first organic compounds to be investigated by the X-ray method. The early work on these crystals afforded evidence that the long axes of the molecules lay along the c direction in the crystal, but less definite indication was obtained regarding the lateral disposition of the molecules. An attempt was made to settle this point by a study of the intensities of the principal X-ray reflections by visual estimate, and this led to a distorted “tetrahedral” structure being advanced. Somewhat later it was shown by Sir William Bragg that this structure was untenable, the discrepancies between the calculated and the measured values of certain reflections being too great. In this work absolute measurements of intensity were obtained for the more important planes, and the evaluation of the atomic positions carried out by Fourier analysis. This led to a structure consisting of molecules with flat or slightly distorted carbon rings, whose planes made an angle of about 25° with the bc plane, and with the long axis of the molecule tilted about 6° away from the direction of the c axis towards a more upright position. Almost at the same time Banerjee independently arrived at a structure, based upon the measurement of some intensities, together with the results of optical and magnetic measurements, which agreed very closely with Bragg’s structure. At the commencement of the present work, then, it could be taken that the structure of anthracene was approximately known. It was very important, however, to confirm these results by more accurate and more extensive intensity measurements, and also to attempt to work out the finer details of the structure. For example, it was not known if the carbon rings were quite flat like the graphite structure, or slightly puckered, perhaps intermediate between the diamond and graphite type: the evidence seemed to point to the latter possibility. The carbon to carbon distance was not accurately known. The only estimate obtained was 1⋅48 A., which is again intermediate between the diamond (1⋅54) and the graphite (1⋅42) distance.

The Interaction of Bio-Molecules with Lipid Membranes Studied by X-ray Diffraction

2014 ◽  
Vol 228 (10-12) ◽  
Author(s):  
Maikel Rheinstädter ◽  
Laura Toppozini ◽  
Hannah Dies
Keyword(s):  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Quantitative Information ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Scattering ◽  
Molecular Ordering ◽  
Indispensable Tool

AbstractFor the past 100 years, X-ray diffraction has been a powerful and indispensable tool to study the structure of matter. The challenge when studying molecular ordering in biological materials is their inherent disorder and strong fluctuations, which often suppress the formation of Bragg peaks. In the case of membranes, X-rays can detect molecules inside and confined between membranes. In this article we review examples to highlight the capabilities and accomplishments of X-ray scattering for the determination of membrane structure. X-ray diffraction gives quantitative information about partitioning of a small molecule, ethanol, in lipid bilayers. By taking amyloid-

Measuring the linearity of X-ray detectors: consequences for absolute attenuation, scattering and absolute Bragg intensities

2011 ◽  
Vol 44 (2) ◽  
pp. 281-286 ◽  
Author(s):  
Zwi Barnea ◽  
Christopher T. Chantler ◽  
Jack L. Glover ◽  
Mark W. Grigg ◽  
M. Tauhidul Islam ◽  
...  
Keyword(s):  
Single Crystals ◽  
Linear Response ◽  
Absolute Intensity ◽  
X Rays ◽  
X Ray ◽  
Intensity Measurements ◽  
Highly Sensitive ◽  
Ion Chambers ◽  
The Absolute ◽  
Order Reflection

The linearity of response of X-ray detectors is tested. Examples of linearity tests demonstrate the remarkable range of linear response of flowing-gas ion chambers in the synchrotron environment. The diagnostic is also highly sensitive to the presence in the X-ray beam of harmonic X-rays diffracted by a higher-order reflection of the monochromator. The remarkable range of linearity of ion chambers has enabled the accurate measurement of the absolute X-ray attenuation of a number of elements. It should now be possible to measure the absolute intensity of Bragg reflections, provided such measurements are carried out with extended-face single crystals. The advantages of the extended-face crystal technique for Bragg intensity measurements are summarized and a number of approaches to absolute Bragg intensity measurement are discussed.

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