Scattering of X-rays and Neutrons

Hoinkis E. Small-angle scattering of neutrons and x-rays from carbons and graphites. In Thrower PA, ed. Chemistry and Physics of Carbon, vol. 25, New York Marcel Dekker. 1997 71-241. 

Small-Angle Scattering of Neutrons and X-rays from Carbons and Graphites, Ernst Hoinkis... 

Hoinkis E. Small-angle scattering of neutrons and X-rays from carbons and graphites. 

William T. Heller obtained his PhD in physics from Rice University in 1999. After postdoctoral training at Los Alamos National Laboratory, he moved to Oak Ridge National Laboratory for additional postdoctoral training before accepting a post as chemist/biophysicist in the Chemical Sciences Division of Oak Ridge National Laboratory. His work entails the application of neutron and x-ray scattering methods to the study of the structure and function of biological macromolecules and the characterization of materials. 

Scattering experiments can be conducted with any kind of radiation (e.g. sound, electromagnetic waves, neutron radiation). This book will be confined to the scattering of light and X-rays, as these two types are most frequentiy used for the characterisation of colloidal suspensions. Both belong to electromagnetic radiation, yet the mechanisms of interaction with matter are completely dUferent. This difference becomes manifest in the refractive indices, which deviate qualitatively. For this reason, both types of radiation are separately discussed. 

The structure of microemulsions have been studied by a variety of experimental means. Scattering experiments yield the droplet size or persistence length (3-6 nm) for nonspherical phases. Small-angle neutron scattering (SANS) [123] and x-ray scattering [124] experiments are appropriate however, the isotopic substitution of D2O for H2O... 

The spectroscopic techniques that have been most frequently used to investigate biomolecular dynamics are those that are commonly available in laboratories, such as nuclear magnetic resonance (NMR), fluorescence, and Mossbauer spectroscopy. In a later chapter the use of NMR, a powerful probe of local motions in macromolecules, is described. Here we examine scattering of X-ray and neutron radiation. Neutrons and X-rays share the property of being found in expensive sources not commonly available in the laboratory. Neutrons are produced by a nuclear reactor or spallation source. X-ray experiments are routinely performed using intense synclirotron radiation, although in favorable cases laboratory sources may also be used. 

The potential of reversed micelles needs to be evaluated by theoretical analysis of the metal ion distribution within micelles, by evaluation of the free energy of the solvated ions in the reversed micelle organic solution and the bulk aqueous water, and by the experimental characterization of reversed micelles by small-angle neutron and x-ray scattering. 

G.D. Wignall, Neutron and X-ray scattering. In J.E. Mark (Ed.), Physical Properties of Polymers Handbook, Springer-Verlag, New York, 1996, p. 299. 

Water on Smectites. Compared to vermiculites, smectites present a more difficult experimental system because of the lack of stacking order of the layers. For these materials, the traditional technique of X-ray diffraction, either using the Bragg or non-Bragg intensities, is of little use. Spectroscopic techniques, especially nuclear magnetic resonance and infrared, as well as neutron and X-ray scattering have provided detailed information about the position of the water molecules, the dynamics of the water molecule motions, and the coordination about the interlayer cations. 

Early studies, which did not include many high-order reflections, revealed systematic differences between spherical-atom X-ray- and neutron-temperature factors (Coppens 1968). Though the spherical-atom approximation of the X-ray treatment is an important contributor to such discrepancies, differences in data-collection temperature (for studies at nonambient temperatures) and systematic errors due to other effects cannot be ignored. For instance, thermal diffuse scattering (TDS) is different for neutrons and X-rays. As the effect of TDS on the Bragg intensities can be mimicked by adjustment of the thermal parameters, systematic differences may occur. Furthermore, since neutron samples must be... 

The scattering of light (including X-rays and neutrons) by a sample is determined by the angular dependence of the phase difference cp of the light re-emitted by all pairs of points in the sample that are illuminated by the incident beam. 

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