Beta decay transition

In nuclear physics, a beta decay transition is the change in state of an atomic nucleus undergoing beta decay. A beta particle and a neutrino are emitted from the nucleus. The final state of the nucleus after the beta decay depends on the spins of the outgoing beta particle and the neutrino. The spins can be either parallel, or anti-parallel. This leads to different types of beta decay transition:

• In a Fermi transition, the spins of the two emitted particles are anti-parallel, for a combined spin ${\displaystyle S=0}$. Spin considerations therefore do not alter the total angular momentum of the nucleus.

• In a Gamow-Teller transition, the spins of the two emitted particles are parallel, with total spin ${\displaystyle S=1}$Spin considerations therefore either alter the total angular momentum of the nucleus by one, or leave it unaltered.

Additionally, the beta particle and neutrino may also carry off orbital angular momentum. These forbidden transitions can occur with both Fermi and Gamow-Teller transitions. While "forbidden" may be a misnomer, these types of transitions have longer lifetimes than the allowed Fermi and Gamow-Teller transitions.

In a given unstable nuclide the transitions may be completely Fermi, completely Gamow, or have both types of transitions occurring. Both transition types occur in both ${\displaystyle \beta ^{+}}$ and ${\displaystyle \beta ^{-}}$ decays.