Diffraction scattered radiation

The 3D MoRSE code is closely related to the molecular transform. The molecular transform is a generalized scattering function. It can be used to predict the intensity of the scattered radiation i for a known molecular structure in X-ray and electron diffraction experiments. The general molecular transform is given by Eq. (22), where i(s) is the intensity of the scattered radiation caused by a collection of N atoms located at points r. ... 

The occurrence of the mesophase in the fiber is confirmed by x-ray diffraction examination. The occurrence of three equatorial reflections 010, 110, and 100, the absence of layer and meridional reflections, and the manifestation of the intensity maximum of diffusively scattered radiation at 20 = 19 in the fiber diffraction pattern are the criterion for the presence of the mesophase. The... 

This chapter deals with the study of structural properties of catalysts and catalytic model surfaces by means of interference effects in scattered radiation. X-ray diffraction is one of the oldest and most frequently applied techniques in catalyst characterization. It is used to identify crystalline phases inside catalysts by means of lattice structural parameters, and to obtain an indication of particle size. Low energy electron diffraction is the surface sensitive analog of XRD, which, however, is only applicable to single crystal surfaces. LEED reveals the structure of surfaces and of ordered adsorbate layers. Both XRD and LEED depend on the constructive interference of radiation that is scattered by relatively large parts of the sample. As a consequence, these techniques require long-range order. 

Multichannel instruments These are equipped with a photodiode array detection system. The radiation from a tungsten or deuterium lamp is focused on the sample or solvent cell, and then passes to a diffracting grating. The scattered radiation arrives at the diode array, which simultaneously detects and analyzes various wavelengths. 

The particular sensitivity of diffuse-reflection spectroscopy to surface structures, is due to the usually multiple reflection and diffraction of radiation at the surfaces of the scattering particles. Therefore catalytic processes and chemically modified surfaces are frequently studied this way. 

X-ray diffraction experiments can be performed either by the energy-dispersive method or the angular dispersive method. In the first case one uses a polychromatic beam and measures the photon energy distribution of the scattered radiation at a constant... 

As a result, there are Bragg reflections with different (but related) indices that have identical intensities, as shown in an hkO X-ray diffraction photograph (Figure 3.15, Chapter 3), where I[hkO) equals I hkO). The only exception to FFiedel s Law is found if atoms scatter radiation anomalously, as described in Chapter 14. 

Placement of the monochromator in the diffracted beam has the advantage of suppressing background radiation originating in the specimen, such as fluorescent radiation and incoherent (Compton modified) scattered radiation. For example, if a steel specimen or any iron-rich material is examined with copper radiation in an ordinary diffractometer, the background due to fluorescent Fe K radiation will be unacceptably high. But if a monochromator is added and oriented to reflect only Cu Aa, the background is reduced practically to zero, because the fluoresced Fe Kol and Fe K(i do not enter the counter. A monochromator may therefore... 

The beam of secondary radiation issuing from the sample consists largely of fluorescent radiation, but there are some other weak components present as well. These are coherent scattered radiation, coherent diffracted radiation, and incoherent (Compton modified) radiation. These components appear as a background on which the spectral lines are superimposed. This background is normally low (see Fig. 15-3), but it may become rather high if the sample contains a large proportion of elements of low atomic number, because the sample will then emit a large amount of Compton modified radiation. 

The structure of pure liquids and liquid solutions is conveniently studied using diffraction techniques [5]. The most common of these is X-ray diffraction. Two other useful techniques are neutron and electron diffraction. In these experiments, radiation, which is usually monoenergetic, penetrates the liquid sample and is scattered through an angle 0 (see fig. 2.6). The analytical information is obtained by studying the intensity of the scattered radiation as a function of this angle. In... 

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