Nuclear Level Density and ${\hat{I}}^3$-ray Strength Function of ${}^{67}\mathrm{Ni}$ and the impact on the i-process

Abstract

Proton-${\hat{I}}^3$ coincidences from $(\mathrm{d},\mathrm{p})$ reactions between a ${}^{66}\mathrm{Ni}$ beam and a deuterated polyethylene target have been analyzed with the inverse-Oslo method to find the nuclear level density (NLD) and ${\hat{I}}^3$-ray strength function (${\hat{I}}^3$SF) of ${}^{67}\mathrm{Ni}$. The ${}^{66}\mathrm{Ni}(n,{\hat{I}}^3)$ capture cross section has been calculated using the Hauser-Feshbach model in TALYS using the measured NLD and ${\hat{I}}^3$SF as constraints. The results confirm that the ${}^{66}\mathrm{Ni}(n,{\hat{I}}^3)$ reaction acts as a bottleneck when relying on one-zone nucleosynthesis calculations. However, the impact of this reaction is strongly dampened in multi-zone models of low-metallicity AGB stars experiencing i-process nucleosynthesis.

Submitted to Phys. Rev. C