Understanding the production of the heaviest elements requires a wealth of information on the nuclear properties of short-lived nuclei. The rapid neutron capture process (r-process) is responsible for the majority of the production of the heaviest elements. The r-process utilizes neutron-capture reactions on heavy, neutron-rich nuclei. The nuclei involved in the r-process are very neutron-rich, short-lived, and very difficult to produce, so little information is known about them. The lack of directly measured neutron-capture cross sections has led to the development of indirect techniques that can be used to reduce the uncertainty in the neutron-capture cross sections, which can vary by orders of magnitude between different calculations. The b-Oslo method is one indirect technique which aims to reduce the uncertainty in the two statistical properties of the nucleus that contribute the largest sources of uncertainty in the r-process calculations: the nuclear level density (NLD) and g-ray strength function (gSF). Both are required to calculate a neutron-capture cross section in the Hauser-Feshbach statistical framework, along with the neutron optical model. The b-Oslo method utilizes decay to populate high-energy excited states in the same nucleus that would have been formed in the neutron-capture reaction of interest. The g rays from the de-excitation are observed in the Summing NaI (SuN) detector to determine the total excitation energy of the nucleus as well as the g-ray cascade to the ground state. With this information, the NLD and gSF can be extracted, after normalization to other data or theoretical calculations. With experimentally constrained NLD and gSF, the overall uncertainty of a neutron-capture cross section has been showed to be significantly reduced.The neutron-capture cross sections of four neutron-rich nuclei (73Zn, 70,71,72Ni) were experimentally constrained using the b-Oslo method. The 73Zn(n,g)74Zn data was also used to compare the constrained neutron-capture cross sections obtained from three different Hauser-Feshbach codes to determine additional sources of systematic uncertainty. The three Ni reactions were also compared to the 68,69Ni cross sections that were previously constrained using the b-Oslo method.
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