In nuclear physics, a beta decay transition is the change in state of an atomic nucleus undergoing beta decay. (β-decay) When undergoing beta decay, a nucleus emits a beta particle and a corresponding neutrino, transforming the original nuclide into one with the same mass, but differing charge. (an isobar)
There are several types of beta decay transition. In a Fermi transition, the spins of the two emitted particles are anti-parallel, for a combined spin . As a result, the total angular momentum of the nucleus is unchanged by the transition. By contrast, in a Gamow-Teller transition, the spins of the two emitted particles are parallel, with total spin , leading to a change in angular momentum between the initial and final states of the nucleus.
The theoretical work in describing these transitions was done between 1934 and 1936 by George Gamow and Edward Teller at George Washington University.