Geiger-counter measurements of Bragg and diffuse scattering of X-rays by single crystals

The advantages and limitations of the use of Geiger counter equipment for the measurement of scattering intensity from small single crystals are discussed, and the effect of the presence of varying amounts of white radiation in the incident and reflected beams is investigated. Crystals of urea and of oxalic acid dihydrate were studied before and after immersion in liquid air, using Cu K and Mo K radiations, with argon- and krypton-filled counter tubes. It was found that the thermal diffuse scattering is independent of crystal perfection. The ratio of thermal scattering intensity to Bragg scattering for a mosaic crystal increases rapidly with angle of scattering when measured for equivalent groups of thermal waves, and is also much greater for Cu than for Mo radiation.