The role of core excitations in the structure and decay of the 16⁺ spin-gap isomer in ⁹⁶Cd

The first evidence for β-delayed proton emission from the 16⁺ spin gap isomer in ⁹⁶Cd is presented. The data were obtained from the Rare Isotope Beam Factory, at the RIKEN Nishina Center, using the BigRIPS spectrometer and the EURICA decay station. β p branching ratios for the ground state and 16⁺ isomer have been extracted along with more precise lifetimes for these states and the lifetime for the ground state decay of ⁹⁵Cd. Large scale shell model (LSSM) calculations have been performed and WKB estimates made for l = 0, 2, 4 proton emission from three resonance-like states in ⁹⁶Ag, that are populated by the β decay of the isomer, and the results compared to the new data. The calculations suggest that l = 2 proton emission from the resonance states, which reside approx 5 MeV above the proton separation energy, dominates the proton decay. The results highlight the importance of core-excited wavefunction components for the 16⁺ state. (authors)