SHAPE COEXISTENCE AND SUPERDEFORMATION IN 28Si

We study shape coexistence of differently deformed states within Si-28 using shell-model and beyond-mean-field techniques. Experimentally, Si-28 exhibits shape coexistence between an oblate ground state and an excited prolate structure. The oblate rotational band is described well within the sd shell using the USDB interaction. However, for the prolate band, a modification of this interaction is required, lowering the single-particle energy of the 1d(3/2) orbital. Furthermore, we explore the possibility of a superdeformed configuration in Si-28. Our calculations, spanning both the sd and pf shells, disfavour the existence of a superdeformed 0(+) bandhead within an excitation energy range of 10-20 MeV.