Alpha vs Beta Decay

Alpha decay emits an alpha particle (a helium-4 nucleus: 2 protons + 2 neutrons) and reduces the parent's mass number by 4 and atomic number by 2. Driven by strong-force binding and quantum tunneling through the Coulomb barrier. Energies typically 4–9 MeV; range in air ~few cm.

Beta decay is mediated by the weak interaction. In β decay a neutron becomes a proton, electron, and antineutrino: n → p + e + ν̅e. In β+ decay a proton becomes a neutron, positron, and neutrino. Beta spectra are continuous because the neutrino carries off variable energy — the observation that led Pauli to predict the neutrino in 1930.

Side-by-side: alpha is heavy and slow (~107 m/s), strongly ionising, stopped by paper. Beta is light and fast (~108 m/s), moderately ionising, stopped by a few mm of aluminium. Gamma decay (photon emission) often follows both.

Recent research on this topic from arXiv

Preprints and papers indexed on arXiv.org. Links open the public abstract pages.

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