Strong neutron- γ competition above the neutron threshold in the decay of Co70

The β -decay intensity of 70 Co was measured for the first time using the technique of total absorption spectroscopy. The large β -decay Q value [12.3(3) MeV] offers a rare opportunity to study β -decay properties in a broad energy range. Two surprising features were observed in the experimental results, namely, the large fragmentation of the β intensity at high energies, as well as the strong competition between γ rays and neutrons, up to more than 2 MeV above the neutron-separation energy. The data are compared to two theoretical calculations: the shell model and the quasiparticle random phase approximation (QRPA). Both models seem to be missing a significant strength at high excitation energies. Possible interpretations of this discrepancy are discussed. The shell model is used for a detailed nuclear structure interpretation and helps to explain the observed γ -neutron competition. The comparison to the QRPA calculations is done as a means to test a model that provides global β -decay properties for astrophysical calculations. Our work demonstrates the importance of performing detailed comparisons to experimental results, beyond the simple half-life comparisons. A realistic and robust description of the β -decay intensity is crucial for our understanding of nuclear structure as well as of r -process nucleosynthesis.