Clustering and Triaxial Deformations of ${}^{40}$Ca

Abstract

We have studied the positive-parity states of ${}^{40}$Ca using antisymmetrized molecular dynamics (AMD) and the generator coordinate method (GCM). Imposing two different kinds of constraints on the variational calculation, we have found various kinds of ${}^{40}\mathrm{Ca}$ structures such as a deformed-shell structure, as well as $\alpha$-${}^{36}$Ar and ${}^{12}$C-${}^{28}$Si cluster structures. After the GCM calculation, we obtained a normal-deformed band and a superdeformed band together with their side bands associated with triaxial deformation. The calculated $B(E2)$ values agreed well with empirical data. It was also found that the normal-deformed and superdeformed bands have a non-negligible $\alpha$-${}^{36}$Ar cluster component and ${}^{12}$C-${}^{28}$Si cluster component, respectively. This leads to the presence of an $\alpha$-${}^{36}$Ar higher-nodal band occurring above the normal-deformed band.

11pages, 9 figures