"Alpha" and "beta" radiation was the description given to the newly-discovered phenomena at the beginning of research into radioactivity. More accurately, the alpha particle is the nucleus of the helium atoms having two protons and two neutrons, and the much higher energy beta particle is an electron released from the atom.
The Fermi theory of beta decay describes the probability of decay, or transition, in terms of the statistics of nuclear forces at the moment of decay. In his calculation, Fermi proposed a new particle, the neutrino, to account for the slight loss of electron energy observed during the process and preserve the principle of conservation of energy.
Twenty-five years after Fermi's theory, detailed understanding of the beta decay mechanism was reached and the theory confirmed.
This theory is also called Fermi's Golden Rule.
Cover page for Fermi and Robinson case files, #3173 and #3174, Final action 1/8/1947. (548K)
Citation of Enrico Fermi for Franklin Medal, 3/10/1947. (2.0M)