Abstract
We have studied positive-parity states of 28Si using antisymmetrized molecular dynamics and multiconfiguration mixing with constrained variation. Applying constraints to the cluster distance and the quadrupole deformation of the variational calculation, we have obtained basis wave functions that have various structures such as α-24Mg and 12C-16O cluster structures as well as deformed structures. Superposing those basis wave functions, we have obtained a oblate ground state band, a β vibration band, a normal-deformed prolate band, and a superdeformed band. It is found that the superdeformed bands contain large amounts of the α-24Mg cluster components. The results also suggest the presence of two excited bands with the developed α-24Mg cluster structure, where the inter-cluster motion and the 24Mg-cluster deformation play important roles.
Highlights
Clustering plays critical roles in excited states of p-shell and very light sd-shell nuclei such as 16O and 20Ne[1, 2]
To understand the mean-field and cluster aspects in the heavier system, 28Si is an important case, because 28Si has a rich variety of structures in its excited states from view points of both clustering and deformations
The β vibration band appears because the oblately deformed state is soft against quadrupole deformation
Summary
Clustering plays critical roles in excited states of p-shell and very light sd-shell nuclei such as 16O and 20Ne[1, 2]. Based on AMD calculations, there has been discussion that both mean-field and cluster aspects play important roles in the excited states of 32S, 40Ca and 44Ti[3,4,5,6]. In the ground state band and the low-lying excited band, the coexistence of the prolate and the oblate deformation has been studied for quite some time. Kubono et al have proposed a largely deformed band called the “excited prolate” band based on a 12C(20Ne, α) reaction[11,12,13]. This band assignment, is not confirmed yet, because intra-band electromagnetic transitions have not been observed. Details of this work was reported in [16]
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