EXOTIC NUCLEI: THE SHELL MODEL VIEW (PART I)

by Prof. Frédéric Nowacki (IPHC Strasbourg)

Friday 12 Jul 2019, 14:30 → 16:30 Europe/Rome

C.VILLI meeting room (INFN-LNL)

In this twofold seminar, I will expose the basics of the shell model description of atomic nuclei and its application to exotic nuclei, in particular at the neutron drip-line.
In this first seminar, the theoretical framework will be be introduced. The basic ingredients of shell-model calculations will be exposed: the relevance of valence spaces, the modern derivation of effective interaction and the numerical challenges in solving the nuclear many-body problem (see [1] for a general review) . Particular emphasis will be put on recent characterization of the effective nuclear interaction and its impact on shell evolution for very neutron rich nuclei.
In a forthcoming second seminar, I will expose some of the latest developments in micro-scopic nuclear structure calculations for exotic nuclei far from stabilitity in the vicinity of 78Ni, in a key region needed for understanding nucleosynthesis paths of gold and some of the most
heavy elements.
Our recent algebraic Nilsson SU3 self-consistent model[2] will be used to describe the intruder relative evolution in the vicinity of 78Ni. The spectroscopy of the exotic nucleus 78 performed at the RIKEN-RIF laboratory in Japan has been recently published in Nature [3]. The re-
sults support the doubly magic character N=50, Z=28, of the heaviest nickel isotope, that is spherical in its ground state. In addition they have detected the presence at very low energy (2.5 MeV) of another facet of the same nucleus which is radically different, characterized by its spheroidal shape. This atypical phenomenon of coexistence, more germane to molecular systems, was predicted by the Configuration-Interaction (LSSM) calculations of the Strasbourg-Madrid collaboration in 2016 [4]. The model predicts as well the vanishing of the magic closure at N=50 for the more exotic isotones of Chromium and Iron which should be deformed in their ground states, leading to the idea of merging islands of collectivity from N=40 to N=50, as already observed from N=20 to N=28 [5, 6]. Core excitations and their impact on moments in Cu and Zn isotopic chains will be discussed. Finally, discussion of the underlying mecanism in terms of Spin-Tensor components will be exposed and compared to other neutron-rich regions of the nuclear chart.

1. E. Caurier, G. Martinez-Pinedo, F. Nowacki, A. Poves, A. P. Zuker, Rev. Mod. Phys. 77, 427 (2005)
2. A. P. Zuker et al., Phys. Rev. C 92, 024320 (2015)
3. R. Tanushui et al., Nature 569, 53-58 (2019)
4. F. Nowacki, A. Poves, Phys. Rev. Lett. 117, 272501 (2016)
5. C. Santamaria et al., Phys. Rev. Lett. C 115, 192501 (2015)
6. E. Caurier, F. Nowacki, A. Poves, Phys. Rev. C 90, 014302 (2014)