Editing Radioactive decay (section)

=== Nucleon emission ===
{{Main|Neutron emission|Cluster emission|Nuclear fission}}
Shortly after the discovery of the neutron in 1932, [[Enrico Fermi]] realized that certain rare beta-decay reactions immediately yield neutrons as an additional decay particle, so called beta-delayed [[neutron emission]]. Neutron emission usually happens from nuclei that are in an excited state, such as the excited <sup>17</sup>O* produced from the beta decay of <sup>17</sup>N. The neutron emission process itself is controlled by the [[nuclear force]] and therefore is extremely fast, sometimes referred to as "nearly instantaneous". Isolated [[proton emission]] was eventually observed in some elements. It was also found that some heavy elements may undergo [[spontaneous fission]] into products that vary in composition. In a phenomenon called [[cluster decay]], specific combinations of neutrons and protons other than alpha particles (helium nuclei) were found to be spontaneously emitted from atoms.