Neutron scattering, the scattering of free neutrons by matter, can refer to either the physical process or the experimental technique which uses this process for the investigation of materials. Neutron scattering as a physical process is of primordial importance in nuclear engineering. Neutron scattering as an experimental technique is used in crystallography, physics, physical chemistry, biophysics, and materials research. It is practiced at research reactors and spallation neutron sources that provide neutron radiation of sufficient intensity. Neutron diffraction (elastic scattering) is used for determining structures; Inelastic neutron scattering is used for the study of atomic vibrations and other excitations.
Neutron scattering techniques are non-destructive, penetrating techniques that allow obtaining unique information on the structure and dynamics of materials. It find uses in many applications ranging from engineering and building, mining, archeology, medicine, food processing and scientific research.
The importance of neutron scattering relies on the fact that neutrons are scattered by atomic nuclei, in contrast to X-rays and electrons which are scattered by atomic electrons. This results in a number of differences, perhaps the most important being in the scattering from light elements. Whereas one electron on a hydrogen atom can be hard to find by X-ray or electron diffraction, the hydrogen nucleus scatters neutrons strongly and is easily found in a neutron diffraction experiment. This is of special importance in biological samples.