Betaminus

Betaminus, often written as beta minus or β− decay, refers to a type of radioactive decay in which a neutron inside an unstable nucleus is transformed into a proton. This conversion increases the atomic number by one, changing the element while leaving the mass number the same. The process is a manifestation of the weak nuclear interaction and is common in neutron-rich nuclides.

In the decay, a neutron converts to a proton, emitting an electron (the beta particle) and an electron antineutrino: n → p + e− + ν̄e. The decay occurs when the daughter nucleus has a lower total energy than the parent, making the process energetically allowed. The emitted electron has a continuous energy spectrum with a maximum energy determined by the mass difference (the Q value) between parent and daughter nuclei. The rate of beta minus decay varies widely among isotopes and is characterized by half-lives that can range from milliseconds to many billions of years. Transitions are categorized as allowed or forbidden, affecting the decay probability.

Betaminus is important in physics and applications. It governs the natural radioactive decay of many isotopes, such as carbon-14, which decays to nitrogen-14 and is used in radiocarbon dating. Beta minus emitters are employed in medicine for radiotherapy and diagnostic tracers, with isotopes like yttrium-90 or lutetium-177 representing common therapeutic examples. In astrophysics, beta minus decay influences nucleosynthesis and the evolution of element abundances in stars and stellar explosions. The term betaminus is a notation variant for beta minus decay noted in some texts as β−.