X-ray scattering and diffraction

X-ray diffraction and scattering are valuable characterization methods. The accuracy of the results, however, depends strongly on the loading of metal in the zeolite. 

Ihble 4-8. EXAFS results characterizing the iridium clusters formed by decarbonylation of [Ir4(CO)i2] in NaY zeolite at 325 °C in He followed by H2. [78] 

X-ray diffraction crystallography can be used to determine not only the framework structures but also the locations of the isolated metal ions in the zeolites. The method is applicable when the metals are periodically isolated within the crystalline zeolite structure and not agglomerate outside of it. Although the method is, in principle, appropriate for the characterization of all types of metal clusters in zeolites, its use has been largely restricted to ionic clusters, [138, 139] which are beyond the scope of the present review. 

The radial electron distribution (RED) determined from X-ray diffraction data has been frequently used to characterize the structures of encaged metal clusters. In contrast to EXAFS spectroscopy, the RED gives only metd-metal distances, not metal-support and metal-adsorbate distances. 

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P. Canton, C. Meneghini, P. Riello, A. Benedetti, in B. M. Weekhuysen (ed.) In-Situ Spectroscopy of Catalysts in X-ray Diffraction and Scattering, American Scientific Publishers, 2004, 281. 

Classical X-ray diffraction and scattering is carried out in the subarea of wide-angle X-ray scattering (WAXS). The corresponding scattering patterns yield information on the arrangement of polymer-chain segments (e.g., orientation of the amorphous phase, crystalline structure, size of crystals, crystal distortions, WAXS crystallinity). 

The excellent characteristics of the IP system as an integrating area detector are well suited to X-ray diffraction and scattering experiments using synchrotron radiation. The system is particularly well suited for biological specimens which require the shortest exposure time or the smallest amount of X-ray dose possible as demonstrated through the applications in this article. 

Table 2 Comparison of Mn- Mn Distances as Determined by X-Ray Diffraction and Scattering and Other Spectroscopic...

In Section 9.3 we present experimental studies of plastic deformation in two semi-crystalline polymers, HDPE and Nylon-6, both in tension and in plane-strain compression flow, from initial spherulitic morphologies to large plastic strains. In these studies, the evolving morphological alterations were monitored closely by a complementary array of techniques involving light microscopy and X-ray diffraction and scattering both in the crystalline and in the amorphous components. 

X-Ray Diffraction and Scattering Methods. With the advent of more powerful and intense X-ray and neutron sources, diffraction and scattering methods have become increasingly more popular for studjdng catalysts in action (18,156,177-182). Both types of radiation are highly penetrating so that again... 

In X-ray diffraction and scattering experiments, several X-ray sources can be employed, from X-ray tubes and rotating anodes to synchrotron radiation. Figure 2 presents in a schematized manner the SAXS setup manipulating collimated beams. An ordinary laboratory SAXS experiment is shown in Fignre 2(a), with a typical size of the beam focused at the detector of the order of a few hundred micrometers. The magnitude of the scattering vector can be written as... 

In this text we have focussed mainly on the combinations from X-ray spectroscopy with X-ray diffraction and scattering in a time regime of 0.1 seconds/data frame and slower. This is a timing regime which is relevant in many materials science-related research fields. Faster XAS experiments are feasible but tend to focus on more fundamental problems in which structure formation is maybe the consequence but not concurrent in time and therefore combinations with X-ray scattering is less obvious. 

Synchrotron radiation based X-ray diffraction and scattering methods have found many uses in the study of structural developments of materials when exposed to external perturbations like pressure, chemical or mechanical changes. The well known method of powder X-ray diffraction (PXRD) or also Wide Angle X-ray Scattering (WAXS) hardly requires any introduction since it is a standard tool in many laboratories and we refer here to the many existing text books that describe the possibilities and limitations of this technique. ... 

Debye was responsible for theoretical treatments of a variety of subjects, including molecular dipole moments (for which the de-bye is a non-SI unit). X-ray diffraction and scattering, and light scattering. His theories relevant to thermodynamics include the temperature dependence of the heat capacity of crystals at a low temperature (Debye crystal theory), adiabatic demagnetization, and the Debye-Huckel theory of electrolyte solutions. In an interview in 1962, Debye said that he... 

Recently, two groups in Paris (10,11) have observed that DNA that is very rich in A-T (>60%) does not show the B- A transition observed with G-C rich DNA. It is significant that this observation was made using two completely different methods, linear dichroism and X-ray diffraction and scattering. Since it is believed that DNA must change to the A form in order to be transcribed (12) (RNA-DNA hybrids are in the A form), these authors concluded that DNA regions containing primarily A-T pairs are not transcribed, but they may be the spacers between cistrons. 

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