Compton scattering is the
inelastic scattering of a
photon by a
charged particle, usually an
electron. It results in a decrease in
energy (increase in
wavelength) of the photon (which may be an
X ray or
gamma ray photon), called the
Compton effect. Part of the energy of the photon is transferred to the recoiling electron.
Inverse Compton scattering exists, in which a charged particle transfers part of its energy to a photon.