Cluster decay

The cluster decay (also cluster emission, English cluster decay ) is a rarely occurring radioactive decay in which a particle heavier than the alpha particle is emitted.

History

The cluster decay was predicted theoretically in 1980 by Aureliu Săndulescu, Dorin N. Poenaru and Walter Greiner. HJ Rose and GA Jones rendered in 1983 at the University of Oxford the first experimental evidence, which was published in the journal Nature in early 1984. They noted that the isotope radium -223 ( an alpha emitter with a half -life of 11.43 days ) with emission of a carbon-14 nucleus can decay directly into lead -209:

Type and occurrence

The cluster decay is observed only at alpha radiant radioactive elements whose atomic number is 87 or higher. Because of this dual occurrence of cluster decay and alpha decay is called in affected nuclides by a dual core decay.

The name " cluster " was chosen because the emitted particles is an " accumulation " (English clusters) of protons and neutrons.

The frequency of such a cluster emission is compared with the alpha -decay in approximately 1:109 to 1:1016. According to previous observations, the emitted clusters have a number of protons 6-16 So there are nuclei of chemical elements whose atomic number is in the range of 6 to 16. The preferred emitted in such a cluster decay clusters are: carbon-14, neon -24, neon -25 and magnesium - 28th

Examples:

In the Karlsruhe nuclide chart from 2006 16 nuclides are listed which can decay by cluster emission. The naturally occurring isotope uranium -234, an alpha emitter, even has three possibilities of the cluster decay - namely, the emission of a neon -24, neon -26- one or a magnesium particle:

Experimentally verified Clusterzerfälle

The following table gives an overview of the experimentally proven Clusterzerfälle with the following information:

  • Decay: Parents core → daughter cluster
  • Magic numbers
  • = Decay energy of the reaction: with = mass defect of parent nucleus and daughter cluster
  • = Logarithm of the half-life

The different types of cluster decay can be well illustrated in a Nukliddiagramm:

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