Investigating the Shell Evolution and Neutron Structure of ⁶⁸Ni through (d,p) and (p,d) Transfer Reactions

by Prabhat Sharma (2^nd year PhD student)

The evolution of nuclear shell structure in exotic nuclei provides key insights into the fundamental nature of nuclear forces. In nuclei far from stability, conventional magic numbers can disappear, while new ones may emerge, a phenomenon known as shell evolution [1]. A well-known example is the evolution of the N=28 shell gap from ⁴⁰Ca to ⁴⁸Ca, which has
been successfully explained by three-nucleon (3N) forces [2]. Similarly, the N=14 shell gap in oxygen isotopes shows a comparable trend [3]. These studies highlight the crucial role of many-body interactions in shaping shell structure.

To extend our understanding to heavier nuclei, we investigate the evolution of the N=50 shell gap for which the isotopic chain of Ni would be the perfect candidate. An experiment was carried out at GANIL to study ⁶⁸Ni via (p,d) and (d,p) reactions, as this nucleus is the anchor point to determine the amplitude of the N=50 shell gap in ⁷⁸Ni, from relatively well known neutron-neutron effective interaction from experimental data. By performing neutron-adding and neutron-removing reactions on ⁶⁸Ni, we also get a unique access to the spectroscopic strengths and thus, the occupancy of the orbitals below and above N=40. This allows to characterize the magicity at N=40. Indeed, depending on whether a sharp occupancy drop is observed or not, the nucleus can be concluded to have either a magic or a superfluid nature [4]. Moreover, it is also planned to deduce the information on the 2p_1/2 – 2p_3/2, 1g_7/2 – 1g_9/2 and 1f_5/2 – 1f_7/2 spin-orbit splittings.

In this seminar, I will present the status of the ongoing analysis and the results obtained so far, with particular emphasis on the (d,p) channel. Some preliminary results on the (p,d) channel will also be presented.

References
[1] O. Sorlin and M.G. Porquet, Prog. Part. Nucl. Phys. 98, 602-673 (2008).
[2] J. D. Holt et al., J. Phys. G: Nucl. Part. Phys. 39, 085111 (2012).
[3] T. Otsuka et al., Phys. Rev. Lett. 105, 032501 (2010).
[4] O.Sorlin, S.Leenhardt, C.Donzaud, J.Duprat, F. Azaiez, et al., Phys. Rev. Lett. 88, 092501 (2002).