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The {\beta} decays of very neutron-rich nuclides in the Co-Zn region were studied experimentally at the National Superconducting Cyclotron Laboratory using the NSCL {\beta}-counting station in conjunction with the neutron detector NERO. We measured the branchings for {\beta}-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., Comment: 13 pages, 13 figures

The �� decays of very neutron-rich nuclides in the Co-Zn region were studied experimentally at the National Superconducting Cyclotron Laboratory using the NSCL ��-counting station in conjunction with the neutron detector NERO. We measured the branchings for ��-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

The impact of nuclear physics on astrophysical r-process models is discussed, emphasizing the importance of beta-decay properties of neutron-rich nuclei. Several r-process motivated beta-decay experiments performed at the National Superconducting Cyclotron Laboratory are presented. The experiments include the measurement of beta-decay half-lives and neutron emission probabilities of nuclei in regions around Ni-78; Se-90; Zr-106 and Rh-120, as well as spectroscopic studies of Pd-120. A summary on the different experimental techniques employed, data analysis, results and impact on model calculations is presented., Comment: 10 pages, 5 figurs, Conference proceeding (PoS)

A value of 0.28 +/- 0.02 s has been deduced for the half-life of the ground state of 60Mn, in sharp contrast to the previously adopted value of 51 +/- 6 s. Access to the low-spin 60Mn ground state was accomplished via beta decay of the 0+ 60Cr parent nuclide. New, low-energy states in 60Mn have been identified from beta-delayed gamma-ray spectroscopy. The new, shorter half-life of 60Mn^g is not suggestive of isospin forbidden beta decay, and new spin and parity assignments of 1+ and 4+ have been adopted for the ground and isomeric beta-decaying states, respectively, of 60Mn., 13 pages, 5 figures, Accepted for publication in Phys. Rev. C

The ground state magnetic moment of 35K has been measured using the technique of nuclear magnetic resonance on beta-emitting nuclei. The short-lived 35K nuclei were produced following the reaction of a 36Ar primary beam of energy 150 MeV/nucleon incident on a Be target. The spin polarization of the 35K nuclei produced at 2 degrees relative to the normal primary beam axis was confirmed. Together with the mirror nucleus 35S, the measurement represents the heaviest T = 3/2 mirror pair for which the spin expectation value has been obtained. A linear behavior of gp vs. gn has been demonstrated for the T = 3/2 known mirror moments and the slope and intercept are consistent with the previous analysis of T = 1/2 mirror pairs., 14 pages, 5 figures

The shell structure underlying shape changes in neutron-rich nuclei between N=20 and N=28 has been investigated by a novel application of the transient field technique to measure the first-excited state g factors in S-38 and S-40 produced as fast radioactive beams. Details of the new methodology are presented. In both S-38 and S-40 there is a fine balance between the proton and neutron contributions to the magnetic moments. Shell model calculations which describe the level schemes and quadrupole properties of these nuclei also give a satisfactory explanation of the g factors. In S-38 the g factor is extremely sensitive to the occupation of the neutron p3/2 orbit above the N=28 shell gap as occupation of this orbit strongly affects the proton configuration. The g factor of deformed S-40 does not resemble that of a conventional collective nucleus because spin contributions are more important than usual., Comment: 10 pages, 36 figures, accepted for publication in Physical Review C

The shell structure underlying shape changes in neutron-rich nuclei near N=28 has been investigated by a novel application of the transient field technique to measure the first-excited state g factors in 38S and 40S produced as fast radioactive beams. There is a fine balance between proton and neutron contributions to the magnetic moments in both nuclei. The g factor of deformed 40S does not resemble that of a conventional collective nucleus because spin contributions are more important than usual., Comment: 10 pages, 6 figures, accepted in PRL

The nuclear magnetic moment of the ground state of 57Cu has been measured to be 2.00 +/- 0.05 nuclear magnetons (nm) using the beta-NMR technique. Together with the known magnetic moment of the mirror partner 57Ni, the spin extraction value was extracted as -0.78 +/- 0.13. This is the heaviest isospin T=1/2 mirror pair above the 40Ca region, for which both ground state magnetic moments have been determined. Shell model calculations in full fp shell giving mu(57Cu)~2.4 nm and ~0.5 imply significant shell breaking at 56Ni with the neutron number N=28., Comment: 4 pages, 3 figures, accepted in PRL

Nuclei with magic numbers serve as important benchmarks in nuclear theory. In addition, neutron-rich nuclei play an important role in the astrophysical rapid neutron-capture process (r-process). 78Ni is the only doubly-magic nucleus that is also an important waiting point in the r-process, and serves as a major bottleneck in the synthesis of heavier elements. The half-life of 78Ni has been experimentally deduced for the first time at the Coupled Cyclotron Facility of the National Superconducting Cyclotron Laboratory at Michigan State University, and was found to be 110 (+100 -60) ms. In the same experiment, a first half-life was deduced for 77Ni of 128 (+27 -33) ms, and more precise half-lives were deduced for 75Ni and 76Ni of 344 (+20 -24) ms and 238 (+15 -18) ms respectively., Comment: 4 pages, 3 figures

The low-energy level structure of the exotic Na isotopes 28,29Na has been investigated through beta-delayed gamma spectroscopy. The N=20 isotones for Z=10-12 are considered to belong to the ``island of inversion'' where intruder configurations dominate the ground state wave function. However, it is an open question as to where and how the transition from normal to intruder-dominated configurations happens in an isotopic chain. The present work, which presents the first detailed spectroscopy of 28,29Na, clearly demonstrates that such a transition in the Na isotopes occurs between 28Na (N=17) and 29Na (N=18), supporting the smaller N=20 shell gap in neutron rich sd shell nuclei. The evidence for inverted shell structure is found in intruder dominated spectroscopy of low-lying states, beta-decay branching ratios and shell model analysis., 4 pages, 4 figures