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Elastic scattering is a form of particlescattering inscattering theory,nuclear physics andparticle physics. In this process, the internal states of theparticles involved stay the same. In the non-relativistic case, where the relative velocities of the particles are much less than thespeed of light, elastic scattering simply means that the totalkinetic energy of the system is conserved.[1] At relativistic velocities, elastic scattering also requires the final state to have the same number of particles as the initial state and for them to be of the same kind.[2]
When the incident particle, such as analpha particle orelectron, isdiffracted in theCoulomb potential ofatoms andmolecules, the elastic scattering process is calledRutherford scattering. In manyelectron 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 elasticelectron scattering becomes the main component of the scattering process and the scattering intensity is expressed as a function of themomentum transfer defined as the difference between the momentum vector of the incident electron and that of the scattered electron.[citation needed]
For particles with the mass of a proton or greater, elastic scattering is one of the main methods by which the particles interact with matter. At relativistic energies, protons, neutrons,helium ions, andHZE ions will undergo numerous elastic collisions before they are dissipated. This is a major concern with many types ofionizing radiation, includinggalactic cosmic rays,solar proton events, free neutrons innuclear weapon design andnuclear reactor design, spaceship design, and the study of theEarth's magnetic field. In designing an effectivebiological shield, proper attention must be made to thelinear energy transfer of the particles as they propagate through the shield. In nuclear reactors, the neutron'smean free path is critical as it undergoes elastic scattering on its way to becoming a slow-movingthermal neutron.[citation needed]
Besides elastic scattering, charged particles also undergo effects from theirelementary charge, which repels them away from nuclei and causes their path to be curved inside anelectric field. Particles can also undergoinelastic scattering and capture due to nuclear reactions. Protons and neutrons do this more often than heavier particles. Neutrons are also capable of causingfission in an incident nucleus. Light nuclei likedeuterium andlithium can combine innuclear fusion.[citation needed]
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