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

Abstract

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 74Co (18 +/- 15%) and 75-77Ni (10 +/- 2.8%, 14 +/- 3.6%, and 30 +/- 24%, respectively) for the first time, and remeasured the Pn values of 77-79Cu, 79,81Zn, and 82Ga. For 77-79Cu and for 81Zn 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 75Co (30 +/- 11 ms) and 80Cu (170+110 -50 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.

13 pages, 13 figures

References in corpus (7)

• The r-process of stellar nucleosynthesis: Astrophysics and nuclear physics achievements and mysteries
• Evolution of the N=50 shell gap energy towards ${}^{78}$Ni
• Beta-decay half-lives and beta-delayed neutron emission probabilities of nuclei in the region below A=110, relevant for the r-process
• Nucleosynthesis Modes in the High-Entropy-Wind of Type II Supernovae: Comparison of Calculations with Halo-Star Observations
• Supernova Fallback: A Possible Site for the r-Process
• Mass measurements beyond the major r-process waiting point 80Zn
• Nucleosynthesis in neutron-rich ejecta from quark-novae

Cited by in corpus (12)

• Current Status of r-Process Nucleosynthesis
• Novel technique for constraining r-process (n,$\gamma$) reaction rates
• New Detections of Arsenic, Selenium, and Other Heavy Elements in Two Metal-Poor Stars
• Horizons: Nuclear Astrophysics in the 2020s and Beyond
• Penning-trap mass spectrometry of highly charged, neutron-rich Rb and Sr isotopes in the vicinity of $A\approx 100$
• Segmented YSO scintillation detectors as a new $\beta$-implant detection tool for decay spectroscopy in fragmentation facilities
• Beta decay of 71,73Co; probing single particle states approaching doubly magic 78Ni
• Fast-timing study of ${}^{81}$Ga from the $\beta$ decay of ${}^{81}$Zn
• Allowed and unique first-forbidden stellar electron emission rates of neutron-rich copper isotopes
• Persistence of the $Z=28$ shell gap in $A=75$ isobars: Identification of a possible $(1/2^{-})$ $\mu$s isomer in ${}^{75}$Co and $\beta$ decay to ${}^{75}$Ni
• The 76Cu conundrum remains unsolved
• Ab initio calculations of beta-decay half-lives for $N=50$ neutron-rich nuclei