Elastic scattering

In scattering theory and in particular in particle physics, elastic scattering is one of the specific forms of scattering. In this process, the energy of the incident particles is conserved, only their direction of propagation is modified (by interaction with other particles and/or a potential).

Electron elastic scattering
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.

Optical elastic scattering
When a photon penetrates into a medium composed of particles whose sizes are much smaller than the wavelength of the incident photon, the scattering process, also known as Rayleigh scattering, is also elastic. In this scattering process, the energy (and therefore the wavelength) of the incident photon is conserved and only its direction is changed. In this case, the scattering intensity is proportional to the fourth power of the reciprocal wavelength of the incident photon. Other types of scattering may occur such as Raman scattering where the scattered photon either gives energy to or takes energy from the medium.