Half-lives and branchings for β-delayed neutron emission for neutron-rich Co-Cu isotopes in the r-process

P. Hosmer, H. Schatz, A. Aprahamian, O. Arndt, R. R.C. Clement, A. Estrade, K. Farouqi, K. L. Kratz, S. N. Liddick, A. F. Lisetskiy, P. F. Mantica, P. Möller, W. F. Mueller, F. Montes, A. C. Morton, M. Ouellette, E. Pellegrini, J. Pereira, B. Pfeiffer, P. ReederP. Santi, M. Steiner, A. Stolz, B. E. Tomlin, W. B. Walters, A. Wöhr

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The β decays of very neutron-rich nuclides in the Co-Zn region were studied experimentally at the National Superconducting Cyclotron Laboratory using the NSCL β-counting station in conjunction with the neutron detector NERO. We measured the branchings for β-delayed neutron emission (Pn values) for Co74 (18±15%) and Ni75-77 (10±2.8%, 14±3.6%, and 30±24%, respectively) for the first time, and remeasured the Pn values of Cu77-79, Zn79,81, and Ga82. For Cu77-79 and for Zn81 we obtain significantly larger Pn values compared to previous work. While the new half-lives for the Ni isotopes from this experiment had been reported before, we present here in addition the first half-life measurements of Co75 (30±11 ms) and Cu80 (170-50+110 ms). Our results are compared with theoretical predictions, and their impact on various types of models for the astrophysical rapid neutron-capture process (r-process) is explored. We find that with our new data, the classical r-process model is better able to reproduce the A=78-80 abundance pattern inferred from the solar abundances. The new data also influence r-process models based on the neutrino-driven high-entropy winds in core collapse supernovae.

Original languageEnglish
Article number025806
JournalPhysical Review C - Nuclear Physics
Issue number2
StatePublished - Aug 18 2010


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