Decay modes heavy elements

There is considerable variety in the modes of decay of heavy elements if spontaneous fission is considered a mode of radioactive decay, then there are many chains that meet this criterion of long-to-short. However, this chapter does not include fission except as a mechanism of terminating a chain. 

Fission of the nucleus, whereby it splits into two roughly equal halves, is accompanied by a huge release of energy. It was first observed by Hahn and Strassman (1939), who were bombarding uranium with neutrons. Many heavy elements are susceptible to induced fission, but spontaneous fission can occur in some of the heaviest elements, and is thought to be the principal mode of decay for the transuranic elements. 

The most familiar form of transmutation is radioactive decay, a natural process in which a nucleus emits a small particle or photon of light. Three common modes of decay are labeled alpha, beta, and gamma (the first three letters of the Greek alphabet). Alpha decay occurs among elements at the heavy end of the periodic table, basically elements heavier... 

Slow neutron reactions general. An elementary extrapolation of the parameters of slow neutron resonances in heavy elements hows that for energies up to 2 Mev and more the levels of the compound nucleus are discrete and do not overlap to any great extent. At low energies, then, there can be little doubt that the interaction of a neutron with a nucleus results in the formation of a compound nucleus and the decay of this nucleus does not reflect its mode of... 

Large, heavy elements, such as uranium and thorium, tend to undergo alpha emission. This decay mode relieves the nucleus of two units of positive charge (two protons) and four units of mass (two protons + two neutrons). What a process. Each time an alpha particle is emitted, four units of mass are lost. 1 wish I could find a diet that would allow me to lose four pounds at a time ... 

Heavy ion emission would be grouped with spontaneous fission and not considered in this chapter were it not for the convenience the chains afford as a source of radioactive materials with which to study the process. Products such as Ra can be produced in charged-particle bombardments, but that implies the presence of energetic ions, which can complicate the detection of a few heavy ions from decay. The ranges of the heavy ions emitted by processes analogous to a decay are a few milligrams per square centimeter. Thin sources are needed, and the carrier-free materials that can be isolated from the chains serve this purpose well. It is likely that heavy particle emission will be found to be a decay mode for most heavy elements. 

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