[en] The very neutron-rich light nuclei provide a fertile testing ground for our understanding of nuclear structure. The resonances in unbound neutron-rich light nuclei are expected to provide important constraints on our understanding of evolution of nuclear shell structure and nuclear binding. Experimentally, this region offers our only practical possibility for detailed spectroscopy of nuclei beyond the neutron drip line. Theoretically, the very light neutron-rich nuclei are capable of being described using ab initio models. In addition, recent advanced shell model approaches, such as, the shell model in the continuum, and the no-core shell model are capable of providing predictions in this region. Therefore, experimental information on them will prove to be useful in forming a complete view of nuclear structure. In addition, the structure of some unbound systems, such as 1^0Li, is key to constructing three-body descriptions of two-neutron halo nuclei. One of the tools most well adapted to the study of nuclei far from stability is that of 'knockout' or breakup of a high-energy radioactive beam. Following a brief description of the technique, two specific topics related to the spectroscopy of light unbound systems will be discussed: A search for the putative low-lying 1/2^- spin-orbit partner of the 7^He(3/2^-) ground state; An investigation of the parity inversion in the N = 7 isotones 9^He and 1^0Li. The talk will conclude with some comments on the need to investigate more fully the structure of 9^He and 1^0Li, and possible future low-energy experiments that could be pursued at TRIUMF.(author)

[en] We report on the study of a new nuclide, ¹⁴F, and on the idea of an experiment to solve the structure mystery of nuclei in the region around ⁹He.

[en] We consider the possible existence of bound states of the multineutron systems ³n, ⁴n, ⁶n, and ⁸n in the framework of the method of angular potential functions. An algorithm is developed for p-shell nuclei with a realistic NN interaction, and is implemented for the trineutron. It is shown that these systems have no bound states

[en] The comparison of the calculated widths of ⁹He with the measured ones shows that: 1) the shell occupation in ⁹He has a normal order (1/2^- - 1/2⁺) contrary to some shell model predictions of the parity inversion; 2) strong core polarization in ⁹He takes place which explains the existence of narrow levels in ⁹He and their absence in ⁷He. (orig.)

No abstract available

[en] Two problems in exotic neutron-rich nuclei are addressed on the basis of microscopic calculations. First, the parity inversion problem in neutron-rich nuclei ¹¹Be and ⁹He in relation with the isospin dependence of the kinetic energies for N=7 isotones, is studied. The ground states of the two nuclei are predicted to be the non-normal positive parity states. Multipole resonances in the nucleus ¹⁰He are discussed in the framework of the self-consistent H-F and RPA theory in order to study the strength distributions

No abstract available

[en] The ¹⁰He nucleus, being a open-quotes maximal neutron-rich nucleusclose quotes in the ratio of neutrons to protons (p:n=1:4) among nuclei observed so far, is investigated within the ⁸He+n+n model. The energy and decay width of the three-body system are solved by applying the complex scaling method to the ⁸He+n+n Hamiltonian, where the folding-type ⁸He-n potential is carefully chosen through the analysis of the experimental resonance energy 1.16 MeV of ⁹He and in comparison with the ⁹Li-n folding potential employed successfully in the description of the loosely bound ¹¹Li system. The calculated result (E_r=1.8 MeV, Γ=1.4 MeV) of the ¹⁰He ground state corresponds well to the observed values. copyright 1997 The American Physical Society

No abstract available

[en] The status of theoretical and experimental investigations on unbound nucleus ⁹He is briefly introduced. The results of modern shell model suggest that the ground state of ⁹He should be 1/2⁺ instead of 1/2^- as expected by the normal shell ordering. Therefore, it means that the parity inversion which was well known in ¹¹Be occurs also in ⁹He ground state. Recently, some resonance states were observed in transfer reactions and final-state reaction, but their spin-parities cannot be exactly determined and the ground-state cannot be uniquely identified. New technique, which is elastic resonance scattering in inverse kinematics, has been used in recent experiments with radioactive ion beam. The authors expect that the new results on ⁹He energy levels will be obtained in ISOL type second-beam line experiments. (authors)