Secondary beams of unstable nuclei with kinetic energies of several hundred MeV per nucleon are produced at, GSI in fragment~ationr eactions followed by in-flight, isot,ope separat'ion. Results of ...studies of light) neutron-rich nuclei ranging from beryllium to oxygen including halo nuclei are presented. Interaction of the projectiles with lead targets leads to Coulomb breakup mediated t,hrough dipole excitabions into the continuum. Non-resonant excitat,ions near the neutron separat,ion threshold deliver information on ground-stat,e properties such as spect,roscopic factors.
The level structures of the N=5083As, 82Ge, and 81Ga isotones have been investigated by means of multi-nucleon transfer reactions. A first experiment was performed with the CLARA–PRISMA setup to ...identify these nuclei. A second experiment was carried out with the GASP array in order to deduce the γ-ray coincidence information. The results obtained on the high-spin states of such nuclei are used to test the stability of the N=50 shell closure in the region of 78Ni (Z=28). The comparison of the experimental level schemes with the shell-model calculations yields an N=50 energy gap value of 4.7(3) MeV at Z=28. This value, in a good agreement with the prediction of the finite-range liquid-drop model as well as with the recent large-scale shell model calculations, does not support a weakening of the N=50 shell gap down to Z=28.
Coulomb breakup of neutron-rich nuclei around mass A ∼ 20 has been studied experimentally using secondary beams (∼ 500–600 MeV/u) of unstable nuclei produced at GSI. The spectroscopic factors deduced ...for the neutron occupying s1/2 level in 15C and 14B ground state is consistent with the earlier reported values. The data analysis for Coulomb breakup of 17C shows that most of the cross section yields the 16C core in its excited state. For 17-22O, the low-lying E1 strength amounts up to about 12% of the energy weighted dipole sum rule strength depending on neutron excess.
Coulomb breakup of neutron-rich nuclei around mass A ∼ 20 has been studied experimentally using secondary beams (∼ 500–600 MeV/u) of unstable nuclei produced at GSI. The spectroscopic factor deduced ...for the neutron occupying s1/2 level in 15C ground state is consistent with the earlier reported value. The data analysis for Coulomb breakup of 17C shows that most of the cross section yields the 16C core in its excited state. For 17–22O, the low-lying E1 strength amounts up to about 12% of the energy weighted dipole sum rule strength depending on neutron excess. The cluster sum rule limit with 16O as a core is almost exhausted for 17,18O, while for more neutron rich isotopes the strength with respect to that limit decreases.
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