X-ray scattering is the redirection of X-rays through interaction with matter. The angular distribution and energy of the outgoing radiation carry information about the material. In elastic scattering the photon energy is unchanged; in inelastic scattering energy is exchanged. X-ray diffraction concerns organized interference of scattered waves, rather than a separate kind of radiation.
The scattering vector compares outgoing and incoming wave vectors. Consider two identical scatterers separated by , each with real elastic scattering amplitude , and neglect multiple scattering. Their amplitude sum and intensity areTwo atoms can therefore scatter strongly in one direction and cancel in another. The measured pattern depends on arrangement, not merely on the number of atoms. For repeating lattice planes in a crystal, constructive interference gives Bragg's law .[ref]
The1913 experiment by William Henry Bragg and William Lawrence Bragg made the angular pattern measurable with a rotating crystal and an ionization chamber in place of a spectrometer telescope. Slits selected a narrow incoming beam; the detector current was measured as its angle changed. Peaks and repeated orders constrained crystal structure and X-ray wavelengths, linking an electrical measurement to atomic-scale geometry.[ref]
The Reflection of X-rays by Crystals by William Henry Bragg and William Lawrence Bragg. pp.428–430 apparatus and angular scan; pp.435–438 reflection orders
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X-ray scattering is a powerful analytical technique used to study the structural properties of materials at the atomic or molecular level. This method involves directing X-rays at a sample and analyzing the way these rays scatter off the material. The scattering of X-rays can provide valuable information about the arrangement of atoms, molecular structures, phase transitions, and other properties of the sample.