Soft dipole resonance in ${}^8$C and its isospin symmetry with ${}^8$He

Abstract

We investigate the soft dipole resonance in the proton-rich nucleus ${}_6^8$C${}_2$, which is a collective dipole oscillation of four valence protons against the $\alpha$ core,and discuss the isospin symmetry with the mirror nucleus ${}_2^8$He${}_6$. We use the $\alpha +N+N+N+N$ five-body cluster model and many-body resonances are obtained using the complex-scaling method. The $1^{-}$ resonance of ${}_6^8$C${}_2$ is confirmed at the excitation energy of 13 MeV with a large decay width of 24 MeV, and its structure is similar to the soft dipole resonance in ${}_2^8$He${}_6$, such as the configuration mixing and the spatial properties. These results indicate a good isospin symmetry in the soft dipole resonances of two nuclei with a common collective excitation of multiproton and multineutron, while the ground states of two nuclei show different properties due to the Coulomb repulsion of valence protons in ${}_6^8$C${}_2$, leading to the symmetry breaking. In conclusion, the appearance of the isospin symmetry differs depending on the states of ${}_6^8$C${}_2$ and ${}_2^8$He${}_6$.

7 pages, 4 figures

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Cited by in corpus (1)

• Physics of many-body resonances with complex scaling and applications to light unstable nuclei