Breakup reactions and exotic structures of halo nuclei

We have performed breakup experiments of halo nuclei: ¹¹Li with a Pb target, ¹⁴Be with ¹²C and proton targets, and ¹⁹C on a proton target at approximately 70 MeV/nucleon at RIKEN. These experiments aim at investigating the E1 response of ¹¹Li, and at searching for the low-lying discrete resonances of ¹⁴Be and ¹⁹C above the neutron decay threshold. The former results shows the strong E1 transitions at low excitation energies (soft E1 excitation), which suggests the spatial neutron-neutron correlation. The latter revealed the first 2⁺ state of ¹⁴Be, and the second 5/2⁺ state of ¹⁹C for the first time. (author)