Properties of neutron-rich $^{\mathrm{71,72,73}}$Ni

The rapid neutron capture process (r-process) is responsible for the synthesis of approximately half of the abundance of the heavy elements. The recent LIGO and Virgo gravitational-wave detection from two colliding neutron stars combined with the wealth of electromagnetic follow-up measurements across the electromagnetic spectrum demonstrated the production of heavy nuclei in an r-process. Despite knowing at least one location for the r-process, many open questions remain. The uncertainties in the nuclear physics inputs present a large barrier to accurately model the abundance distributions in large-scale nucleosynthesis calculations. In particular, neutron-capture rates are the most uncertain theoretical input and the most diffcult to measure directly. The $\beta $-Oslo method is one indirect approach for constraining the neutron-capture cross section. The $\beta $ decay of a short-lived nucleus is used to populate the high-energy states in a daughter nucleus and the subsequent photon deexcitation is monitored and used to infer the nuclear level density (NLD) and the $\gamma $-ray strength function ($\gamma $SF). The NLD and $\gamma $SF are then input into a Hauser-Feshbach model to constrain the neutron capture cross section. A series of experiments have been performed at the National Superconducting Cyclotron Laboratory along the Ni elemental chain. The preliminary results obtained for $^{\mathrm{71,72,73}}$Ni will be presented.