Delayed nuclear radiation can occur in a nuclear decay. It happens when an isotope decays into a very short-lived isotope and then decays again to a relatively long-lived isotope. The short-lived isotope is usually a meta-stable nuclear isomer. Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles. ... Isotopes are forms of an element whose nuclei have the same atomic number–-the number of protons in the nucleus--but different atomic masses because they contain different numbers of neutrons. ... A nuclear isomer is a metastable or isomeric state of an atom caused by the excitation of a proton or neutron in its nucleus so that it requires a change in spin before it can release its extra energy. ...

For example, Gallium-73 decays via beta decay into Germanium-73m which is very short-lived. The Germanium isotope emits two weak gamma rays and a conversion electron. In nuclear physics, beta decay (sometimes called neutron decay) is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted. ... This article is about electromagnetic radiation. ... Conversion electron. ...

Because the middle isotope is so short-lived, the gamma rays are considered part of the Gallium decay. Therefore the above equation is simplified.

However, since there is a short time delay between the beta decay and the high energy gamma emissions and the third and fourth gamma rays, it is said that the lower energy gamma rays are delayed.

Delayed gamma emissions are the most common form of delayed radiation but it is not the only form. It is common for the short-lived isotopes to have delayed emissions of various particles. In these cases it is commonly called a beta-delayed emission. This is because the decay is delayed until a beta decay takes place. For instance nitrogen-17 emits two beta-delayed neutrons after its primary beta emission. Just as in the above delayed gamma emission, the nitrogen is not the actual source of the neutrons, a short lived isotope of oxygen is. Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ...

See also

• Delayed neutron