Jose Javier Valiente Dobon (INFN-LNL)
The magic numbers, originated by the large shell gaps in the energy spectrum of the single-particle states, represent a fundamental quantity governing nuclear structure. They can be reproduced using a single-particle harmonic oscillator potential with a strong spin-ortbit interaction and they are predicted to change for large N/Z ratios. Exotic nuclei close to the shell closures on the neutron drip-line play an important role on nuclear shell structure studies since they allow to search for possible modifications of magic numbers with increasing N/Z ratio. The tensor component, one of the non-central components of the effective nucleon-nucleon interaction, is expected to modify the relative single particle energies when one goes further from stability on the neutron drip line [1,2]. It is expected an attraction for orbitals with anti-parallel spin configuration and a repulsion for orbitals with parallel spin configuration. The change of the shell structure due to the tensor mechanism has been recently discussed in different mass regions [3, 4]. The magic numbers at N=20 and 28 disappear with increasing neutron number and new magic numbers at N=14, 16 and 32 seem to appear. It is also predicted that the Z=28 gap for protons in the pf-shell becomes smaller moving from 68Ni to 78Ni as a result of the attraction between the f5/2 and the g9/2 orbits and repulsion between the f7/2 and g9/2 configurations. In the case of Cu isotopes the changing of effective single-particle energies comes directly from the attraction between the πf5/2 and the υg9/2 orbits and the repulsion between the πf7/2 and the υg9/2 orbits. Recent calculations in the fpg shell seems to indicate that the Z=28 shell gap gets reduced by about 0.7 MeV when filling the neutron g9/2 orbital . The same Shell Model calculations together with the effect of the tensor force performed for the neutron-rich Cu isotopes predict a lowering of the πf5/2 state causing an inversion of the πf5/2 -πp3/2 effective single-particle states when approaching 78Ni. This inversion has been recently confirmed by nuclear spin and magnetic moment measurements for 75Cu by identifying its spin of the ground state as I= 5/2 . Aim of the present proposal is to identify experimentally the location of such low-lying excitations as test of the microscopic interaction in the fpg shell model space. Unlikely to its neighboring isotope 75Cu , no evidence for isomerism was found in 77Cu according to the fragmentation study of 86Kr at 140 MeV/a at the Coupled Cyclotron Facility of NSCL/MSU . Therefore, the nuclei of interest will be populated via beta-decay of the 77Ni through the in flight fragmentation of 86Kr beam at 350 MeV/nucleon. Fragments will be separated in-flight using the BigRIPS facility. The detailed information on the experimental settings will be given in the presentation.  T. Otsuka et al., Phys.Rev.Lett.87 (2001) 082502.  T. Otsuka et al., Prog.Theor.Phys. Supp.146 (2002) 6.  T. Otsuka et al., Phys.Rev.Lett.95 (2005) 232502.  H. Grawe et al., Springer Lect. Notes in Phys. 651, (2004).  K.Sieja and F. Nowacki, Phys. Rev. C 81, 061303 R (2010). K.T. Flanagan et al., Phys. Rev. Lett. 103, 142501 (2009).  J.M Daugas et al., Phys. Rev. C 81, 034304 (2010).  D. S. Cross et al., private communication.