Superallowed beta decay
= Superallowed beta decay
An especially strong <allowed beta decay>, conventionally including pure <Fermi transitions> between $0^+$ <isobaric analog states>. Those states have closely related spatial and spin structure, so the <isospin> ladder operator has a large overlap. A $0^+\to0^+$ assignment alone fixes the allowed Fermi character, but does not establish analog-state overlap or a large rate; a small <comparative half-life> supplies additional evidence.