Low-Spin Structure of ⁵⁸Cu and its Impact on the ⁵⁷Ni(p,γ)⁵⁸Cu Reaction in the νp-Process

Antineutrino interactions can have an important impact on the final composition following explosive nucleosynthesis. During the νp process free neutrons are created and drive the composition toward stability via neutron reactions. Such extreme conditions may be found in environments like the dynamic ejecta of core-collapse or magneto-rotational supernovae. Uncertainties in the ⁵⁷Ni(p,γ)⁵⁸Cu reaction rate have shown a significant impact on astrophysical models and the final isotopic abundances in such scenarios. The low-lying level structure of ⁵⁸Cu (N=Z) and the high-spin structure have been well studied. However, low-spin resonance states above the proton separation energy (S_p= 2.87 MeV), which can dominate the (p,γ) reaction rate, have yet to be measured or have large uncertainties. We conducted a high-resolution γγ-coincidence experiment at ATLAS using Gammasphere coupled to Neutron Shell. Low-spin states in ⁵⁸Cu were preferentially populated via the ⁵⁸Ni(p,n)⁵⁸Cu reaction using a 17-MeV proton beam and deduced from gamma-ray angular distributions. We have identified many relevant low-spin levels with high excitation energy, covering most of the Gamow window. These data are used to constrain the astrophysical ⁵⁷Ni(p,γ)⁵⁸Cu reaction rate and reduce uncertainties in modeling the impact of the νp process. These results will be discussed as well as their influence explored within a single zone nuclear reaction model.