Monochromatic still exposure

The diffraction spots lie on curved arcs where each curve corresponds to the intersection with a him of a cone. With a hat him the intersections 

As far as the geometry is concerned we build on the monochromatic still geometry as outlined in the previous section. 

26 Angle of deviation of the reflected beam with respect to the incident beam 

T The angle between the projections of 0 and onto the equatorial plane 

The following special cases commonly occur (a) /u—0, normal-beam rotation method, then  

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In third-generation synchrotrons, the x-rays are generated in intense flashes of 100 picoseconds (ps) duration. If, dnring this time, an entire diffraction pattern is recorded, the time resolution equals 100 ps (Szebenyi et al. 1992 Srajer et al. 1996, Schotte et al. 2003). However, the traditional monochromatic oscillation diffraction method cannot be used since there is no way to rotate the crystal during this 100 ps timeframe to collect the integrated intensity of a Bragg reflection. Still exposures, therefore, have to be used. 

You can see from Fig. 9.8 that a Laue diffraction pattern is much more complex than a diffraction pattern from monochromatic X rays. But modern software can index Laue patterns and thus allow accurate measurement of many diffraction intensities from a single brief pulse of X rays through a still crystal. If the crystal has high symmetry and is oriented properly, a full data set can in theory be collected in a single brief X-ray exposure. In practice, this approach usually does not provide sufficiently accurate intensities because the data lack the redundancy necessary for high accuracy. Multiple exposures at multiple orientations are the rule. 

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