β-decay strengths of Co isotopes from total absorption spectroscopy

Recent multi-messenger observations of GW170817 have provided evidence of r-process nucleosynthesis in neutron-star mergers. While progress has been made in understanding a site of this critical process, sensitivity studies show that the final abundance distributions of r-process nuclei are greatly impacted by β-decay properties. More specifically, β-delayed neutron-emission can affect the flow back to stability and enrich the environment with neutrons for further neutron capture. While it is assumed that neutron emission dominates above the neutron threshold, recent measurements of β-decay on r-process nuclei observed γ-emission above the neutron threshold. This competition may effect the final abundances of r-process nuclei. For this reason, β-decay intensities for ^69,71Co were measured using the technique of total absorption spectroscopy at the NSCL. The resultant β-decay intensities and deduced Gamow-Teller strengths are compared to QRPA calculations, which are commonly used in r-process calculations. The experimental results of these odd-mass isotopes contain some feeding above the neutron separation energy, though not as strong as observed in ⁷⁰Co, which has then motivated further investigation into the mechanism that is driving the observed n-γ competition.