X-ray diffraction

Method of studying the atomic and molecular structure of crystalline substances by using X-rays. X-rays directed at such substances spread out as they pass through the crystals owing to diffraction (the slight spreading of waves around the edge of an opaque object) of the rays around the atoms. By using measurements of the position and intensity of the diffracted waves, it is possible to calculate the shape and size of the atoms in the crystal. The method has been used to study substances such as DNA that are found in living material.