Diffractometer automatic

The X-ray diffraction studies have not only helped in elucidating the complete structure of a compound in its crystalline state but also in establishing its configuration. The noteworthy feature of the method is that no recourse is taken to chemical work. Thus the structure of the alkaloid the-lepogine, C20 H31NO has been settled without chemical work. For the last two decades the method has been widely employed because it takes less time due to the use of automatic diffractometers and electronic computers. 

These three questions will be examined in relation to the conformational data which have been given by recent carbohydrate crystal structure determinations. Because of the added reliability and accuracy arising from the use of automatic diffractometers only those numerical data will be quoted where these instruments were used. 

The torsion angle data on earlier structures completed prior to the use of automatic diffractometers are reported elsewhere U ). 

Crystals of Xe(OSeFs)2 are rhombohedral, space group R3m. At 23.5 C the hexagonal axes are fl - 6 = 8.588 (3) and c - 11.918 (3) A Z = 3, da cd = 3.345 g cm"3, and V = 761.23 AL The molecule lies on a threefold axis, and there is orientational disorder of the oxygen and fluorine positions. X-ray diffraction data obtained with an automatic diffractometer were analyzed on the basis of a molecular model with some constraints based on chemical considerations to reduce the number of independent parameters of the poorly resolved oxygen and fluorine atoms. For 122 unique reflections with > a(F ) and with anisotropic thermal parameters, R = 0.064. Bond distances are Xe-0 2.12 (5), Se-0 1.53 (5), and Se-F = 1.70 (2) A (uncorrected) and Se-F = 1.77 A (corrected for thermal motion). 

In fact, digital computers and automatic diffractometers have simplified the process of crystal structure analysis to the point where there is no reason, other than reluctance to... 

Note the possibility of completely automatic sample identification by using the tape output of an automatic diffractometer as the input to a computer searching the data file [7.6]. 

Automatic diffractometers can be easily programmed to measure integrated intensity, and Kelly and Short [7.2] have described automated austenite measurements. 

The intensities of all 5579 unique reflections were measured with automatic diffractometer "SYNTEX P2j", using graphitemonochromatized MoK radiation (the 0-20 scan technique, of scan speed was 5 deg/min, no... 

Conformation and structure of A-block in solid state Infrared spectra of solid films of the samples cast from solution were measured with a Shimazu Modjl-30 A IR spectrophotometer in a region of 4000 to 400 cm. X-ray diagrams were obtained by using Ni-filtered Cu Ka radiation, setting a flat surface of the film parallel to a reflecting surface with an automatic diffractometer. For the electron microscopy measurement, thin films cast from solution were stained with osmium tetroxide and examined by transmission microscopy. 

Single crystal X-ray analysis consists of measuring diffraction intensities while rotating a crystal (to ensure the diffraction condition for as many reciprocal spots as possible), by using a computer-controlled automatic diffractometer and obtaining the electron density distribution p(x, y, z) from the inverse relation of EQN (3),... 

Results are achieved rapidly and with much better precision when automatic diffractometers are used to record diffraction data. The X-ray tube furnishes the radiation directly (filters are generally used to obtain more nearly monochromatic radiation). The diffracting crystal is replaced by a powdered or metallic sample. To increase the randomness of orientation in the crystallites, the sample can be rotated in its own plane, that is, the plane perpendicular to the bisector of the angle between the source and detector beams. Note also that as the sample is rotated in the other plane to sweep through various 0 angles, the detector must be rotated twice as rapidly to maintain the angle 20 with the irradiating beam. 

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