Type: Article
Publication Date: 2011-11-03
Citations: 72
DOI: https://doi.org/10.1103/physrevc.84.054304
The structure of low-energy collective states in proton-deficient $N=28$ isotones is analyzed using structure models based on the relativistic energy density functional DD-PC1. The relativistic Hartree-Bogoliubov model for triaxial nuclei is used to calculate binding energy maps in the $\ensuremath{\beta}$-$\ensuremath{\gamma}$ plane. The evolution of neutron and proton single-particle levels with quadrupole deformation, and the occurrence of gaps around the Fermi surface, provide a simple microscopic interpretation of the onset of deformation and shape coexistence. Starting from self-consistent constrained energy surfaces calculated with the functional DD-PC1, a collective Hamiltonian for quadrupole vibrations and rotations is employed in the analysis of excitation spectra and transition rates of ${}^{46}$Ar, ${}^{44}$S, and ${}^{42}$Si. The results are compared to available data, and previous studies based either on the mean-field approach or large-scale shell-model calculations. The present study is particularly focused on ${}^{44}$S, for which data have recently been reported that indicate pronounced shape coexistence.