First direct measurement of Cu-59(p, alpha) Ni-56: A step towards constraining the Ni-Cu cycle in the cosmos

AbstraktAbstract

Reactions on 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 Cu-59(p, alpha) Ni-56 and Cu-59(p, gamma) Zn-60, could potentially halt the production of heavier elements. Here, we report the first direct measurement of Cu-59(p, alpha) Ni-56 using a reaccelerated Cu-59 beam and a cryogenic solid hydrogen target. Our results show that the reaction proceeds predominantly to the ground state of Ni-56, and the experimental rate has been found to be lower than Hauser Feshbach based statistical model predictions. New results hints that the vp process could operate at higher temperatures than previously inferred and therefore remains a viable site for synthesizing the heavier elements.

Reactions on 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 Cu-59(p, alpha) Ni-56 and Cu-59(p, gamma) Zn-60, could potentially halt the production of heavier elements. Here, we report the first direct measurement of Cu-59(p, alpha) Ni-56 using a reaccelerated Cu-59 beam and a cryogenic solid hydrogen target. Our results show that the reaction proceeds predominantly to the ground state of Ni-56, and the experimental rate has been found to be lower than Hauser Feshbach based statistical model predictions. New results hints that the vp process could operate at higher temperatures than previously inferred and therefore remains a viable site for synthesizing the heavier elements.