Laue diffraction techniques

The time-of-flight Laue diffraction technique used at pulsed sources samples a large three-dimensional volume of reciprocal space in a single measurement with a stationary crystal and detector. This is due to the combination of the wavelength sorting inherent in the time-of-flight (TOP) technique with large area position-sensitive detectors (PSDs). 

The five years since last considering specifically recent developments in X-ray and neutron diffraction methods for zeolites [1] have witnessed substantial progress. Some techniques, such as high resolution powder X-ray diffraction using synchrotron X-rays, have blossomed from earliest demonstrations of feasibility to widespread and productive application. Others, such as neutron powder diffraction, have shown steady progress. For still others, notably microcrystal diffraction, a variety of circumstances have contributed to extended gestation periods. Additionally, opportunities scarcely considered earlier (such as single crystal Laue diffraction, and certain developments in computer simulations that complement diffraction work) now command broad attention and warrant the commitment of substantial further investment. 

Now I return to X-ray diffraction to describe probably the oldest type of diffraction experiment, but one whose stock has soared with the advent of synchrotron radiation and powerful computer techniques for the analysis of complex diffraction data. The method, Laue diffraction, is already realizing its promise as a means to determine the structures of short-lived reaction intermediates. This method is sometimes called time-resolved crystallography, implying an attempt to take snapshots of a chemical reaction or physical change in progress. 

Specimens were extracted from the deformed samples at different radii from the cylinder axis, along the torsion axis direction. Some of the diffraction analyses were performed using a hard X-ray diffraction technique developped at Institut Laue Langevin, others were observed via synchrotron X-ray diffraction topography at ESRF (European Synchrotron Radiation Facilities) on the "ID19" beamline. 

Wes] X-ray diffraction studies (Laue, rotation techniques), optical microscopy, chemical analysis W2pe4C phase containing alloys... 

Chemists often make use of the observed shapes of crystals to help in the identification of substances. The description of the shapes of crystals is part of the subject of the science of crystallography. The method of studying the structure of crystals by the diffraction of x-rays, which was discovered by the German physicist Max von Laue (1879-1960) in 1912 and developed by the British physicists W. H. Bragg (1862-1942) and W. L. Bragg (1890-1971), has become especially valuable in recent decades. Much of the information about molecular structure that is given in this book has been obtained by the x-ray diffraction technique. 

Different X-ray diffraction techniques for single crystal starting from Laue techniques to rotation/oscillation and finally to Weissenberg techniques are discussed along with the interpretation and the advantages and limitations. These techniques which are systematically introduced and discussed are essential for imderstanding the inside of structure and their arrangements in a crystal. 

Bulk X-ray diffiraction, thus averaging the X-ray difiiraction signal over a large amount of sample ( mm ), ex situ or under operando conditions can be considered a standard technique using laboratory based or synchrotron based sources. Countless findings rely on the precise description of the atomic order obtained from Laue diffraction patterns to describe structure, phases, reaction pathways, strain, disorder etc. 

Laue Method for Macromolecule X-Ray Diffraction. As indicated above it is possible to determine the stmctures of macromolecules from x-ray diffraction however, it normally takes a relatively long period of data collection time (even at synchrotrons) to collect all of the data. A new technique, the Laue method, can be used to collect all of the data in a fraction of a second. Instead of using monochromated x-rays, a wide spectmm of incident x-rays is used. In this case, all of the reflections that ate diffracted on to an area detector are recorded at just one setting of the detector and the crystal. By collecting many complete data sets over a short period of time, the Laue method can be used to foUow the reaction of an enzyme with its substrate. This technique caimot be used with conventional x-ray sources. 

The techniques of X-ray diffraction analyses of crystals of compounds of interest can be used to determine, with high precision, the three-dimensional arrangement of atoms, ions and molecules in such crystals (14) in each case the result is referred to as the "crystal structure." X-ray diffraction by crystals was discovered by von Laue, Friedrich and Knipping (15) and the technique was applied by the Braggs to the determination of the structures of... 

If this is the case, the technique is then called X-ray diffraction. The wavelength of the X-rays is on the order of 0.1 nm and the diffraction pattern produced is also called a Laue pattern (see Section 5.2.3). 

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