For a system with excess neutrons, the neutron is transformed into a proton and in the process an electron and an antineutrino are emitted. The emitted negatively charged beta particles, usually denoted as - , have a continuum of energies from zero to a maximum energy denoted by E max . Gamma rays are photons emitted during nuclear de-excitation processes. These gamma-ray transitions may be from a metastable excited state, or between levels in a daughter nucleus. This process leaves a K-shell vacancy, and a characteristic x ray from the daughter nucleus can be emitted as orbital electrons from higher shells fill the vacancy.
Annihilation radiation is a form of photon radiation associated with a class of radioactive decays.
Positrons, since they are antiparticles of ordinary electrons, cannot survive long in normal matter. Thus, positrons emitted during radioactive decay will slow down in matter until they reach thermal equilibrium. Bremsstrahlung is the photon radiation emitted by the deceleration of an electron in the Coulomb field of an atom. In the photoelectric process , which dominates at lower energies, the photon transfers its energy to an atomic electron, which is then ejected from the atom with an energy equal to that of the incident photon minus the electron's binding energy. Higher energy photons willundergo multiple Compton scatter events until the process is finally terminated by a photoelectric absorption.