Low-energy cluster modes in N=Z nuclei

Abstract

Significant transition strength in light $\ensuremath{\alpha}$-conjugate nuclei at low energy, typically below 10 MeV, has been observed in many experiments. In this work the isoscalar low-energy response of $N=Z$ nuclei is explored using the finite amplitude method based on the microscopic framework of nuclear energy density functionals. Depending on the multipolarity of the excitation and the equilibrium deformation of a particular isotope, the low-energy strength functions display prominent peaks that can be attributed to cluster mode structures: $\ensuremath{\alpha}+^{12}\mathrm{C}+\ensuremath{\alpha}$ and $\ensuremath{\alpha}+^{16}\mathrm{O}$ in $^{20}\mathrm{Ne}, ^{12}\mathrm{C}+^{12}\mathrm{C}$ in $^{24}\mathrm{Mg}, 4\ensuremath{\alpha}+^{12}\mathrm{C}$ in $^{28}\mathrm{Si}$, etc. Such cluster modes are favored in light nuclei with large deformation.