Reactions on the proton-rich nuclides drive the nucleosynthesis in Core-Collapse Supernovae (CCSNe) and in X-ray bursts (XRBs). CCSNe eject the nucleosynthesis products to the interstellar medium and hence are a potential inventory of p-nuclei, whereas in XRBs nucleosynthesis powers the light curves. In both astrophysical sites the Ni-Cu cycle, which features a competition between $^{ 59}$Cu(p,$\alpha$)$^{ 56}$Ni and $^{ 59}$Cu(p,$\gamma$)$^{ 60}$Zn, could potentially halt the production of heavier elements. Here, we report the first direct measurement of $^{ 59}$Cu(p,$\alpha$)$^{ 56}$Ni using a re-accelerated $^{ 59}$Cu beam and cryogenic solid hydrogen target. Our results show that the reaction proceeds predominantly to the ground state of $^{ 56}$Ni and the experimental rate has been found to be lower than Hauser-Feshbach-based statistical predictions. New results hint that the $\nu p$-process could operate at higher temperatures than previously inferred and therefore remains a viable site for synthesizing the heavier elements.
Categories: nucl-ex