Elastic scattering - Definition

In particle physics, elastic scattering is one of the specific forms of scattering. In this process, the energy of the incident photon or particle (electron, positron, or neutron) is conserved and its propagating direction is changed by the potential of the target.

When an electron is an incident particle and it is diffracted in the Coulomb potential of atoms and molecules, the elastic scattering process is called Rutherford scattering. In many electron diffraction techniques like reflection high energy electron diffraction (RHEED), transmission electron diffraction (TED), and gas electron diffraction (GED), where the incident electrons have sufficiently high energy (>10 keV), the elastic electron scattering becomes the main component of the scattering process and the scattering intensity is expressed as a function of the momentum transfer defined as the difference between the momentum vector of the incident electron and that of the scattered electron.

When a photon penetrates into a medium composed of atoms and molecules whose sizes are much smaller than the wavelength of the incident photon, the scattering process becomes elastic scattering and is called Rayleigh scattering. In this scattering process, the energy and the wavelength of the incident photon are conserved and the direction is changed. In this case, the scattering intensity is proportional to the fourth power of the reciprocal wavelength of the incident photon.