Alpha and proton radioactivity above tin-100

Article By:

Rykaczewski, Krzysztof P. Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee.

Grzywacz, Robert K. Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee.

Last reviewed:2009

DOI:https://doi.org/10.1036/1097-8542.YB090096

Only 263 nonradioactive nuclei occur naturally. These isotopes of various elements are the combinations of Z protons and N neutrons that are the most stable. In all other nuclei, including about 3000 known today, the ratio of proton-to-neutron numbers is nonoptimal, and the isotopes decay to more stable ones, emitting several kinds of radiation. The terms proton radioactivity and alpha radioactivity refer to the spontaneous emission of a charged particle, either a single proton or an alpha (α) particle, from an atomic nucleus. A clustering of two protons and two neutrons is needed to create an alpha particle inside an atomic nucleus, before its emission. This so-called preformation probability reduces the alpha emission rate. Even today, 100 years after understanding of the nature of alpha particles was achieved, the dynamics of the preformation of the alpha particle inside the atomic nucleus is not well understood.

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