Nuclear structure and β decay properties of astrophysical significant A = 56 isobars

Abstract

This study explores the ground-state properties and weak transition rates of $A$=56 isobars including ⁵⁶Ni, ⁵⁶Co, ⁵⁶Fe, ⁵⁶Mn, ⁵⁶Cr and ⁵⁶V. The nuclear ground-state properties of selected nuclei were examined using the relativistic mean field (RMF) model. The RMF model with density-dependent interactions DDME2 and DDPC1 is utilized to analyze the deformation parameters, potential energy curves and surfaces, neutron skin thickness, neutron separation energies and nuclear radii. The deformation parameter computed via the RMF model is then utilized as an input parameter in the proton–neutron quasiparticle random phase approximation (pn-QRPA) model for the analysis of the Gamow–Teller (GT) strength distributions, half-lives and the stellar rates. The computed GT strength distributions align well with the experimental values and the predicted $\beta$ decay half-lives are within factor 10 of the measured data. Stellar rates [(${\beta }^{+}+EC$) and (${\beta }^{-}+PC$)] were computed and compared with earlier computations based on the large-scale shell model (LSSM) and the independent particle model (IPM). For selected isobars, at high-density regime with increasing core temperature, the (${\beta }^{+}+EC$) rates calculated using the pn-QRPA model were up to an order of magnitude lower than those obtained with the LSSM and IPM models. The computed (${\beta }^{-}+PC$) rates were up to six orders of magnitude smaller than those obtained from the LSSM and IPM calculations. The computed stellar rates could provide valuable inputs for $rp$-process nucleosynthesis simulations of the post-core silicon burning phases in stellar evolution.