Elastic scattering

Elastic scattering is an interaction in which the participants’ total kinetic energy is conserved and their internal states remain unchanged, though their directions or momenta may change.

Conservation of momentum: The total momentum of an isolated system remains constant during its evolution. Together with energy conservation, it constrains the outgoing momenta in an elastic collision.
Inelastic scattering: Scattering in which kinetic energy is transferred into internal excitation or other channels. It differs because the outgoing participants can have changed internal states or reduced kinetic energy.
Rutherford scattering: The large-angle scattering of alpha particles by atomic nuclei, used to infer concentrated positive charge. Its elastic events exposed the compact nuclear structure of atoms.
Kinetic energy: The energy associated with an object's motion. Its conservation is part of the defining condition for elastic scattering.
Scattering angle: The angle between an incoming particle’s direction and its outgoing direction after scattering. It describes how strongly elastic scattering redirects an incident particle.
Raman scattering: Inelastic scattering of light that shifts photon frequency through energy exchange with matter. Its frequency shift signals an internal energy change absent in elastic light scattering.
Neutron scattering: Experimental methods that use neutron interactions to investigate the structure and dynamics of matter. Elastic neutron measurements reveal static arrangements of atoms and magnetic moments.
Internal energy: Energy stored in a system’s microscopic motions, interactions, and internal degrees of freedom. Unchanged internal energy distinguishes elastic events from excitation or de-excitation.
Differential cross section: A measure of scattering probability per unit solid angle, often expressed as a function of angle. It quantifies the angular distribution of elastically scattered particles.
Compton scattering: Scattering of a photon by a charged particle that changes the photon’s wavelength and transfers energy. The energy transfer makes this process inelastic for the photon-particle system’s internal channel.

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