Speaker
Prof.
Takaharu Otsuka
(University of Tokyo)
Description
The shell evolution can create various structure patterns, of which the closed-shell structure is of particular interest. Obviously, the closed shell appears if the proton and neutron numbers coincide with magic numbers. It has been known that magic numbers vary as a consequence of the shell evolution due to nuclear forces. Thus, it is of much importance to find where the closed shell appears on the nuclear chart. The 2+ energy systematics can be a good indicator of the closed shell. On the other hand, the 2+ level reflects many aspects of nuclear forces as well as the shell structure. It is therefore crucial to have additional quantity as a measure of the magicity. We recently proposed “magic index”. This quantity implies how much fraction of the ground-state wave function is composed of the closed-shell configuration. Since correlations occur in shell-model wave functions in general, the magic index cannot be 100%. It depends also on the model space. Within a common or similar model space, the magic index can make sense. For instance, the magic index shows interesting variation among three double-magic nuclei $^{56,68,78}$Ni. It shows rather high value for
$^{52,54}$Ca, while their 2+ level is not as high as $^{48}$Ca. As the magic index can be measured as spectroscopic factors, it may provide many interesting cases with transfer reactions.
Primary author
Prof.
Takaharu Otsuka
(University of Tokyo)
