Delayed nuclear radiation
Encyclopedia
Delayed nuclear radiation is a form of nuclear decay. When an isotope
decays into a very short-lived isotope and then decays again to a relatively long-lived isotope, the products of the second decay are delayed. The short-lived isotope is usually a meta-stable nuclear isomer
.
For example, Gallium-73 decays via beta decay
into Germanium-73m2, which is short-lived (499ms). The Germanium isotope emits two weak gamma ray
s and a conversion electron.
Because the middle isotope is so short-lived, the gamma rays are considered part of the Gallium decay. Therefore the above equations are combined.
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 are 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 neutron
s 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.
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
decays into a very short-lived isotope and then decays again to a relatively long-lived isotope, the products of the second decay are delayed. The short-lived isotope is usually a meta-stable nuclear isomer
Nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons . "Metastable" refers to the fact that these excited states have half-lives more than 100 to 1000 times the half-lives of the other possible excited nuclear states...
.
For example, Gallium-73 decays via beta decay
Beta decay
In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...
into Germanium-73m2, which is short-lived (499ms). The Germanium isotope emits two weak gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
s and a conversion electron.
- → + 2 + ; → + (53.4keV) + (13.3keV) +
Because the middle isotope is so short-lived, the gamma rays are considered part of the Gallium decay. Therefore the above equations are combined.
- → + 4 + 2
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 are 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 neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
s after its primary beta emission. Just as in the above delayed gamma emission, the nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
is not the actual source of the neutrons, a short lived isotope of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
is.