Evidence for Subshell atZ=96

Abstract

The evidence is decisive that major nuclear shells are completed at 82 protons and 126 neutrons (both represented by the nuclide Pb{sup 208}) and these, along with major shells at 82 neutrons and certain lower nucleon numbers (N or Z = 20, 28, 50), are well explained by the strong spin orbit coupling model of Mayer and Haxel, Jensen, and Suess. This model suggests the filling of quantum states at certain intermediate points, and there is an accumulating amount of evidence that such 'sub shells' are also discernible, for example, at Z = 58 and Z = 64. The evidence from alpha radioactivity, both (1) the effect of the nuclear radius shrinkage on the relationship between energy and half-life and (2) the discontinuities in the plots of energy vs. mass number at constant Z, gives a striking indication of the closing of major shells at Z = 82 and N = 126. Application of these sensitive criteria as tests for the much smaller 'subshell' effects in the regions Z > 82 and N > 126 leads to some evidence for such a subshell at Z = 96 (curium).