Spectroscopy of neutron-rich nuclei using re-accelerated beams and direct reactions at TRIUMF

Nuclei with large neutron-proton asymmetry unfold unconventional structures like neutron skin and halo and changes in the evolution of nuclear orbitals leading to disappearance of known shell closures and emergence of new ones. In regions where shells closures disappear coexisting diverse nuclear shapes can appear in closely spaced 0⁺ states in even-even nuclei. These unexpected features challenge nuclear models allowing to constrain our understanding of the nuclear force.

The thick neutron surface in neutron-rich nuclei also can give rise to new forms of collectivity at very low-excitation energy, called the soft dipole resonance. While dipole peaks below the giant dipole resonance have been seen in heavier neutron-rich Ni and Sn isotopes, they are at energies relatively high energies ~ 10 MeV. The dipole resonance at low-energy ~ 1 MeV has been observed in ¹¹Li which opens the question if other drip-line nuclei exhibit this phenomenon.

​We will present recent results from reaction spectroscopy studies with re-accelerated beams and the IRIS facility with solid D₂ target at TRIUMF. The (d,p) transfer reaction results will be presented that brings new insight on the levels and shape evolution in neutron-rich ⁹⁴Kr. Spectroscopic studies of ¹¹Li and ⁸He with inelastic scattering will also be presented to explore the quadrupole collectivity and search for soft dipole resonance in ⁸He.