Single crystals camera

G.36 A. J. C. Wilson. Elements of X-Ray Crystallography (Reading, Mass. Addison-Wesley, 1970). Powder cameras and diffractometers single-crystal cameras and diffractometers structure determination diffraction by imperfect crystals. 

Chaudri et al (Ref 21) claim to have observed an unexpectedly high detonation velocity of about 8km/sec for single crystals of cr-lead azide of 2 x 2mm cross-section. They used a framing camera at a framing rate of 5 x 106 sec 1 for their measurements. Frequently it is difficult to obtain reliable quantitative data by this method... 

When the Gandolfi camera is used, a single crystal or crystal fragment is mounted on a glass capillary (Refs 11 19). This camera is thus of great value when a very small amount of the phase to be investigated is available... 

Figure 6. Top single-crystal rotation diagram recorded on Weis-senherg camera from a single crystal inside a glass capillary. Bottom second layer line of Weissenberg photograph of a single...

Recently, a detailed study4,5 of AB02 compounds confirms that AgFe02 has the CuFe02 (delafossite) structure. The cell dimensions, determined with a Guinier camera, are found to be a = 3.0391 2 A. and c = 18.590 2 A. Single crystals are used to measure resistivity as a function of temperature.6 Silver fer-rate(III) exhibits semiconductor behavior with an activation energy of 0.7 e.V. An unusual anisotropy in resistivity is found withp(j c) = 3 X 107 S2-cm. and P( c) = 2 X 1010 J2-cm. 

An interesting study by Schulz et al (Ref 78) used laser light in conjunction with a fast streak camera and Raman spectroscopy to follow the decompn of single crystal RDX at ISOkbar input press. Four regions were distinguished ... 

X-ray and calorimetric data show that structural changes can occur in TNT on heating and that different forms can be prepared by crystallization and sublimation (Ref 36). Differences in the X-ray diffraction patterns of TNT were shown to be based on the method of preparation of TNT (Ref 35), Post-expin debris were examined by a Gandolfi camera, requiring but a single crystal of TNT of micron size for identification purposes (Ref 149). The X-ray diffraction patterns of TNT are included, together with those of Hexanitrostilbene (Ref 94)... 

The EPR/ENDOR measurements described here have been performed on single crystals which are accurately oriented with an x-ray precession camera, x-ray irradiated, and observed at ca. 10 K. The schematic diagram of the X-band EPR apparatus is shown in Figure 18-1 [12], This cavity is a modification of one previously described by Weil et al. [13], The EPR cavity is essentially a cast epoxy, wire wound TE011 cylindrical cavity with external 100 kHz modulation coils. The Cryo-Tip portion of the cavity can be raised 6 cm for x-irradiation and subsequently lowered into the microwave cavity for EPR measurements [14], In the microwave cavity the lowest temperature of the sample is approximately 6 K. However in the irradiation position the lowest temperature is about 10 K because the sample is not as effectively heat-shielded from the room temperature vacuum shroud. 

Fig. 20.30 Rock sample image recorded with a digital camera. In the red circle, the region wet with Ag colloid is highlighted. The micro-SERS spectrum is compared with the normal Raman spectrum of a pyroxene single crystal. Exciting line 785 nm...

The X-ray powder diffraction pattern of cephalothin is presented in Table I. Data were obtained using copper radiation and nickel filter with a camera 11 1.6 mm in diameter. Indexing of the powder pattern was done on the basis of single crystal rotation patterns around both the a and axes, and a wavelength of 1.5 18 x. was used in the calculations. 

The x-ray spectrometer can also be used as a tool in diffraction analysis. This instrument is known as a diffractometer when it is used with x-rays of known wavelength to determine the unknown spacing of crystal planes, and as a spectrometer in the reverse case, when crystal planes of known spacing are used to determine unknown wavelengths. The diffractometer is always used with monochromatic radiation and measurements may be made on either single crystals or polycrystalline specimens in the latter case, it functions much like a Debye-Scherrer camera... 

The purest kind of radiation to use in a diffraction experiment is radiation which has itself been diffracted, since it is entirely monochromatic. If a single crystal is set to reflect the strong A"a component of the general radiation from an x-ray tube and this reflected beam is used as the incident beam in a diffraction camera, then the causes of background radiation listed under (1) and (2) above can be... 

G.39 Harold P. Klug and Leroy E. Alexander. X-Ray Diffraction Procedures, 2nd ed. (New York Wiley, 1974). Contains a great deal of useful detail on the theory and operation of powder cameras and diffractometers. Covers the following topics in depth chemical analysis by diffraction, parameter measurement, line-broadening analysis, texture determination, stress measurement, and studies of amorphous materials. Single-crystal methods are not included. 

The first two-dimensional detector in X-ray diffraction was conventional film. It remained for decades the detector of choice for both single crystal as well as powder diffraction experiments. In the field of two-dimensional detection it was surpassed initially by image plates and later by CCD cameras (Figure 14.1). Today virtually no film is in use, with perhaps the exception of Polaroid used for single-crystal images. To be able to compare various detectors with one another, and to select the most appropriate detector for a specific experiment, certain key technical qualities are important. These are in general the detective quantum efficiency, the spatial response characteristics, the size, speed and dynamic range. ... 

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