Background Beta-decay spectroscopy provides valuable nuclear physics input for thermonuclear reaction rates of astrophysical interest and stringent test for shell-model theories far from the stability line.Purpose The available decay properties of proton drip-line nucleus 27 S are insufficient to constrain the properties of the key resonance in 26 Si(p, γ) 27 P reaction rate and probe the possible mirror asymmetry. The decay scheme of 27 S is complicated and far from being understood, which has motivated but also presented substantial challenges for our experiment.Method The 27 S ions were implanted into a double-sided silicon strip detector array surrounded by the high-purity germanium detectors, where the β-delayed protons and γ rays were measured simultaneously.
ResultsThe precise half-life of 27 S, the excitation energies, β-feeding intensities, log f t values, and B(GT) values for the states of 27 P populated in the β decay of 27 S are determined. The improved spectroscopic properties including are compared to the mirror β decay of 27 Na and to the shell-model calculations using the recently-developed USD * interaction. The present work has expanded greatly on the previously established decay scheme of 27 S.
ConclusionsThe precise mass excess of 27 P, the energy and the ratio between γ and proton partial widths of the 3/2 + resonance were obtained, thereby determining the 26 Si(p, γ) 27 P reaction rate based mainly on experimental constraints. The first experimental evidence for the observation of mirror asymmetries for the transitions in the decays of 27 S and 27 Na is also provided. The shell-model calculations with the Hamiltonians including the modifications on single-particle energies and two-body matrix elements related to the proton 1s 1/2 orbit give a better description of the spectroscopic properties.