57Zn β-delayed proton emission establishes the 56Ni rp-process waiting point bypass

M. Saxena, W. J Ong, Z. Meisel, D. E.M. Hoff, N. Smirnova, P. C. Bender, S. P. Burcher, M. P. Carpenter, J. J. Carroll, A. Chester, C. J. Chiara, R. Conaway, P. A. Copp, B. P. Crider, J. Derkin, A. Estradé, G. Hamad, J. T. Harke, R. Jain, H. JayatissaS. N. Liddick, B. Longfellow, M. Mogannam, F. Montes, N. Nepal, T. H. Ogunbeku, A. L. Richard, H. Schatz, D. Soltesz, S. K. Subedi, I. Sultana, A. S. Tamashiro, V. Tripathi, Y. Xiao, R. Zink

Research output: Contribution to journalArticlepeer-review


We measured the Zn57 β-delayed proton (βp) and γ emission at the National Superconducting Cyclotron Laboratory. We find a Zn57 half-life of 43.6±0.2 ms, βp branching ratio of (84.7±1.4)%, and identify four transitions corresponding to the exotic β-γ-p decay mode, the second such identification in the fp-shell. The p/γ ratio was used to correct for isospin mixing while determining the Zn57 mass via the isobaric multiplet mass equation. Previously, it was uncertain as to whether the rp-process flow could bypass the textbook waiting point Ni56 for astrophysical conditions relevant to Type-I X-ray bursts. Our results definitively establish the existence of the Ni56 bypass, with 14-17% of the rp-process flow taking this route.

Original languageEnglish
Article number137059
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
StatePublished - Jun 10 2022


  • Type-1 X-ray bursts
  • Waiting-point
  • β-decay measurement of proton rich isotope


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