Soft Dipole Resonances in 8He and 8C

Abstract

Soft dipole resonances in 8He and 8C are investigated by applying the complex scaling method to the α + N + N + N + N five-body model for the isospin T = 2 system. The 1− excited resonant states are calculated at (Ex, Γ) = (14.0, 21.1) MeV and (12.7, 24.0) MeV for 8He and 8C, respectively. From the analyses of the configuration mixing and the spatial properties, the soft dipole resonances of two nuclei are understood to be the vibrational states of valence nucleons and the α core. They are also seen to have a good isospin symmetry. In contrast, the ground states of two nuclei show different spatial properties indicating the symmetry breaking due to the Coulomb repulsion of valence protons in 86C2.