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Transmission Geometry (transmission + geometry)
Selected AbstractsA simple and inexpensive capillary furnace for variable-temperature X-ray diffractionJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2008Christine Lavigueur An inexpensive capillary furnace has been developed for variable-temperature X-ray diffraction in transmission geometry of air-stable liquid crystals and other materials. It offers temperature control with fluctuations of less than ±1,K in the range of interest for these samples, from room temperature to near 573,K. Phases can be accessed through heating or cooling with no significant overshooting of the target temperature. The furnace is designed to fit on a classical goniometer, and can be controlled by any standard temperature controller. The simple design of this furnace means that it is both inexpensive to build and easy to operate. [source] Modeling of transmitted X-ray intensity variation with sample thickness and solid fraction in glycine compactsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2003Wenjin Cao Abstract The previous paper in this series introduced an X-ray diffraction quantitation method for the polymorphic content in tablets made of pure components. Before the method could be transferred, further studies were required to explain the commonly observed X-ray intensity variation in analyzing compacts. The literature typically attributes the variation to partial amorphization under compression and/or to preferred orientation, without much viable explanation or compelling evidence. In this study, changes in intensity in compacts analyzed in transmission geometry were found to be primarily a function of sample thickness and solid fraction. A theoretical model was developed to describe the X-ray powder diffraction (XRPD) intensity as a function of solid fraction, mass absorption coefficient, and thickness. The model was tested on two sets of glycine compacts: one with varying thickness at constant solid fraction, and the other with various solid fractions at a given thickness. The results show that the model predicts the XRPD intensity at any given sample thickness and solid fraction. With this model, the intensity variation of compacts made under different compression conditions can be normalized, making the method transferable to various tablet geometries and facilitating the analysis over expected ranges of formulation and process variation. © 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:2345,2353, 2003 [source] Use of a hexapod in diffraction measurements of substrate-supported crystals of organic semiconductorsJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2009Lin Yang Thin films of organic semiconductor prepared on substrates generally contain crystals that have one common crystal plane parallel to the substrate but random in-plane orientations. In diffraction measurements of these structures, it is often required to anchor the X-ray beam on a fixed spot on the sample, such as an optically visible crystallite or island. Here, a hexapod is used in place of a traditional multi-circle diffractometer to perform area-detector-based diffraction measurements on an actual device that contains 6,13-bis(triisopropylsilyethynyl)-pentacene (TIPS-pentacene) crystals. The hexapod allows for sample rotations about any user-defined rotation center. Two types of complex sample motions have been programmed to characterize the structure of the TIPS-pentacene crystal: an in-plane powder average has been performed at a fixed grazing-incident angle to determine the lattice parameters of the crystal; then the in-plane component of the scattering vector was continuously rotated in transmission geometry to determine the local crystal orientation. [source] Plane-wave X-ray topography and its application at SPring-8JOURNAL OF SYNCHROTRON RADIATION, Issue 3 2002Satoshi Iida Plane-wave X-ray topography experiments were carried out at a 200,m-long beamline, BL20B2, at SPring-8. Relatively high-energy X-rays of 30,keV with an angular divergence of about 0.01,arcsec were produced by using only one collimator crystal. FZ-Si and CZ-Si wafers were characterized in transmission geometry (Laue case). Clear oscillatory profiles in rocking curves of the FZ-Si crystal were observed. Plane-wave topographic images of dislocations, growth striations and grown-in microdefects in the CZ-Si crystals were obtained. The dependence of the topographic images of the lattice defects on the sample,photoplate distance was also studied. [source] Two-color pump,probe experiments on silicon inverse opalsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2006C. Becker Abstract We present time-resolved pump,probe experiments in a transmission geometry using off-resonant excitation on very high-quality silicon inverse opals. We show that the nonlinear optical response can drastically be modified by tempering of the sample. The as-grown samples are dominated by an absorptive response with recovery times as short as one picosecond. For the tempered samples, both the relaxation and the scattering times increase, leading to a prominent dispersive response. The data reveal a transient blue-shift of the fundamental stop band on the order of 150 nm with transmission changes as large as a factor of five. Based on simple calculations using the Drude model we estimate corresponding refractive index changes as large as ,n = ,0.5 + i0.07. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||