5He radioactivity

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Abstract
The disintegration of a metastable nuclear state by emission of a light particle can be considered to be a very asymmetric fission process. An approximation of the potential barrier in the overlapping region of the two fragments leads to an analytic relationship for the life-time, allowing us to handle a large number of cases to search for new kinds of radioactivities. In this way, it is predicted that some nuclei with Z = 83-92, N = 127-137 and 97-105,145-157 are able to decay spontaneously by emission of 5 He particles. A tentative optimistic estimation leads to the result that only 15 radionuclides should have partial life-times in the range 10 14-1038 years; all others, except some superheavies, are longer lived. The best candidate is 213Po for which the daughter is a double magic nucleus. Smaller life-times, with a better chance to be experimentally confirmed have some β-delayed 5He emitters, as for example 155Yb, 175Pt, 209-217Ra, 9-11Be, 13-14B, 13-17C and 19-21O