Our understanding of the nuclear structure has dramatically changed over the last 30 years. We are not longer believing in universal magic numbers. In this seminar we will discuss the nuclear structure of these exotic nuclei from an experimentalist approach. The general idea will be to understand what are the similarities and differences between the N = 28 and N = 82 areas of the nuclear chart close to the 48Ca and 132Sn doubly magic nuclei, and what are the physical phenomenons observed there.
The N = 28 area is one of the clearest cases in the nuclear chart where the proton-neutron residual interaction drives the development of deformation. This deformation in the N = 28 isotones is favored by quadrupole excitations across the neutron N = 28 and proton Z = 14 shell gaps added to shell gap reduction, allowing the intruder con guration to become the ground state. The 44S, located in the transitional area between the spherical 48Ca and the deformed 42Si, is a key nucleus to understand how the deformation sets on. Two different experiments performed at GANIL, isomer and in-beam spectroscopy experiment, focused on the study of 44S will be presented, both set of data provide complementary information of the structure of the latter nucleus and therefore information of the nuclear forces involved in this area.
The next question to be raised is whether such a disappearance of the spin-orbit magic numbers persist in heavier systems. The N = 82 region near the doubly-magic 132Sn nucleus is particularly well suited to investigate this phenomenon due to its close analogy with the N = 28 area. The study of the 131In and 130Cd nuclei in an isomer spectroscopy experiment performed at GSI will shed light on the possible shape evolution of the N = 82 isotones and will be discussed in the seminar. The evolution of the N = 82 shell gap can be caused not only due to the proton-neutron residual interaction, but as well due to a modi cation of the nuclear forces due to the neutron excess. Indeed, when reaching the drip line, this excess of neutrons may modify the spin-orbit coupling strength due to the strong interaction between weakly bound orbitals and the continuum. A change of the N = 82 shell gap with the binding energy is envisaged a lower masses, i.e. 122Zr. To access this nucleus experimentally is at the moment and for some years impossible. On the other hand, it is possible to produce lighter nuclear systems were the phenomena expected at 122Zr can be studied. The 24F and 26F nuclei are excellent candidates for this purpose. Recent preliminary results of in-beam and -decay experiments focused on these nuclei will be presented.
