In-beam ␥-ray spectroscopy using fragmentation reactions of both stable and radioactive beams has been performed in order to study the structure of excited states in neutron-rich oxygen isotopes with masses ranging from A = 20 to 24. For the produced fragments, ␥-ray energies, intensities, and ␥-␥ coincidences have been measured. Based on this information new level schemes are proposed for

The structure of 17−20 6 C nuclei was investigated by means of the in-beam γ-ray spectroscopy technique using fragmentation reactions of radioactive beams. Based on particle-γ and particle-γγ coincidence data, level schemes are constructed for the neutron rich 17−20 C nuclei. The systematics of the first excited 2 + states in the Carbon isotopes is extended for the first time to A=20 showing that in contrast to the case of the oxygen isotopes, the N =14 subshell closure disappears. Experimental results are compared with shell-model calculations. Agreement between them is found only if a reduced neutron-neutron effective interaction is used. Implications of this reduced interaction in some properties of weakly bound neutron-rich Carbon are discussed. The formation of nuclear shell gaps, as well as their collapse in certain regions of the chart of nuclides is largely being investigated worldwide. It impacts many unique features in nuclear physics as the abundance of the stable elements in the universe, the possible existence of an island of super heavy nuclei, the route of heavy nuclei to fission and the existence of cluster configurations.It is a remarkable fact that the shell (or subshell) gaps, such 14, 28, 50 and to a weaker extent 82 and 126 share a common origin. Taking for instance the neutron shell gaps, they are formed by the combined action of the spin-orbit (SO) force and by neutron-neutron interactions. The former force significantly over binds the orbit in which the angular momentum and intrinsic spin are aligned (denoted as ↑ ). In addition, the filling of neutrons inside this orbit amplifies its binding due to the attractive neutron-neutron V nn ↑ ↑

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The structure of the 24 F nucleus has been studied at GANIL using the β decay of 24 O and the inbeam γ-ray spectroscopy from the fragmentation of 27,28 Na, 25,26 Ne and 29,30 Mg nuclei. Combining these complementary experimental techniques, the level scheme of 24 F has been constructed up to 3.6 MeV by means of particle-γ and particle-γγ coincidence relations. Experimental results are compared to shell-model calculations using the standard USDA and USDB interactions as well as abinitio valence-space Hamiltonians calculated from the in-medium similarity renormalization group based on chiral two-and three-nucleon forces. Both methods reproduce the measured level spacings well, and this close agreement allows unidentified spins and parities to be consistently assigned.