Gamma decay

Gamma decay is the emission of a high-energy photon when an excited atomic nucleus transitions to a lower-energy state. It changes the nucleus’s energy but usually not its proton or neutron count.

Nuclear isomer: An excited nuclear state with a measurable lifetime longer than typical nuclear excited states. Long-lived isomers can release their stored excitation energy through delayed gamma decay.
Atomic nucleus: The dense central region of an atom, composed of protons and neutrons bound by the strong interaction. Gamma decay occurs when this system moves between internal energy states.
Alpha decay: A radioactive decay in which a nucleus emits a helium-4 nucleus. Unlike gamma decay, alpha decay changes the parent nucleus’s proton and neutron counts.
Mössbauer effect: The recoil-free emission and resonant absorption of gamma rays by nuclei bound in solids. Suppressing recoil allows exceptionally precise measurements of nuclear transition energies.
Internal conversion: A nuclear transition that transfers excitation energy to an atomic electron, ejecting it instead of emitting a photon. It competes with gamma emission by carrying away the same nuclear transition energy.
Nuclear energy level: A quantized energy state of an atomic nucleus. Gamma decay connects two such states, with the energy difference setting the photon energy.
Beta decay: A nuclear transformation that changes a neutron into a proton or a proton into a neutron, emitting a beta particle and a neutrino or antineutrino. Beta decay changes nuclear composition; gamma decay typically only removes excitation energy.
Nuclear medicine: The medical use of radioactive substances and nuclear techniques for diagnosis and treatment. Gamma-emitting radionuclides provide signals that can be detected outside the body.
Gamma-ray spectroscopy: The measurement and analysis of gamma-ray energies and intensities to identify nuclear transitions and isotopes. Observed photon energies reveal the spacing of the nucleus’s excited states.
Photon: The quantum of the electromagnetic field, carrying energy and momentum. The emitted gamma ray is a photon produced by a nuclear transition.

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