The low-lying energy levels of proton-rich 56Cu have been extracted using in-beam γ-ray spectroscopy with the state-of-the-art γ-ray tracking array GRETINA in conjunction with the S800 spectrograph at the National Superconducting Cyclotron Laboratory at Michigan State University. Excited states in 56Cu serve as resonances in the 55Ni(p,γ)56Cu reaction, which is a part of the rp-process in type I x-ray bursts. To resolve existing ambiguities in the reaction Q-value, a more localized IMME mass fit is used resulting in Q=639±82~keV. We derive the first experimentally-constrained thermonuclear reaction rate for 55Ni(p,γ)56Cu. We find that, with this new rate, the rp-process may bypass the 56Ni waiting point via the 55Ni(p,γ) reaction for typical x-ray burst conditions with a branching of up to ∼40%. We also identify additional nuclear physics uncertainties that need to be addressed before drawing final conclusions about the rp-process reaction flow in the 56Ni region.
@article{arxiv.1704.07941,
title = {Low-lying level structure of $^{56}$Cu and its implications on the rp process},
author = {W-J. Ong and C. Langer and F. Montes and A. Aprahamian and D. W. Bardayan and D. Bazin and B. A. Brown and J. Browne and H. Crawford and R. Cyburt and E. B. Deleeuw and C. Domingo-Pardo and A. Gade and S. George and P. Hosmer and L. Keek and A. Kontos and I-Y. Lee and A. Lemasson and E. Lunderberg and Y. Maeda and M. Matos and Z. Meisel and S. Noji and F. M. Nunes and A. Nystrom and G. Perdikakis and J. Pereira and S. J. Quinn and F. Recchia and H. Schatz and M. Scott and K. Siegl and A. Simon and M. Smith and A. Spyrou and J. Stevens and S. R. Stroberg and D. Weisshaar and J. Wheeler and K. Wimmer and R. G. T. Zegers},
journal= {arXiv preprint arXiv:1704.07941},
year = {2017}
}