The neutron-deficient 196,198 Pb isotopes have been studied in Coulomb-excitation experiments employing the Miniball γ-ray spectrometer and radioactive ion beams from the REX-ISOLDE post-accelerator ...at CERN. The reduced transition probabilities of the first excited 2+ states in 196Pb and 198Pb nuclei have been measured for the first time. Values of B ( E 2 ) = 18.2 − 4.1 + 4.8 W.u. and B ( E 2 ) = 13.1 − 3.5 + 4.9 W.u., were obtained, respectively. The experiment sheds light on the development of collectivity when moving from the regime governed by the generalised seniority scheme to a region, where intruding structures, associated with different deformed shapes, start to come down in energy and approach the spherical ground state.
Single-neutron states in the Z=30, N=49 isotope 79Zn have been populated using the 78Zn(d, p)79Zn transfer reaction at REX-ISOLDE, CERN. The experimental setup allowed the combined detection of ...protons ejected in the reaction, and of γ rays emitted by 79Zn. The analysis reveals that the lowest excited states populated in the reaction lie at approximately 1 MeV of excitation, and involve neutron orbits above the N=50 shell gap. From the analysis of γ -ray data and of proton angular distributions, characteristic of the amount of angular momentum transferred, a 5/2+ configuration was assigned to a state at 983 keV. Comparison with large-scale-shell-model calculations supports a robust neutron N=50 shell-closure for 78Ni. Finally, these data constitute an important step towards the understanding of the magicity of 78Ni and of the structure of nuclei in the region.
In-gas-cell laser ionization spectroscopy studies on the neutron deficient 97–101Ag isotopes have been performed with the LISOL setup. Magnetic dipole moments and mean-square charge radii have been ...determined for the first time with the exception of 101Ag, which was found in good agreement with previous experimental values. The reported results allow tentatively assigning the spin of 97,99Ag to 92 and confirming the presence of an isomeric state in these two isotopes, whose collapsed hyperfine structure suggests a spin of 12. The effect of the N=50 shell closure is not only manifested in the magnetic moments but also in the evolution of the mean-square charge radii of the isotopes investigated, in accordance with the spherical droplet model predictions.
Sub-barrier Coulomb excitation was performed on a mixed beam of
62
Mn and
62
Fe, following in-trap
β
−
decay of
62
Mn at REX-ISOLDE, CERN. The trapping and charge breeding times were varied in order ...to alter the composition of the beam, which was measured by means of an ionisation chamber at the zero-angle position of the Miniball array. A new transition was observed at 418 keV, which has been tentatively associated to a (2
+
,3
+
)→ 1
g.s.
+
transition. This fixes the relative positions of the
β
-decaying 4
+
and 1
+
states in
62
Mn for the first time. Population of the 2
1
+
state was observed in
62
Fe and the cross-section determined by normalisation to the
109
Ag target excitation, confirming the
B
(
E
2) value measured in recoil-distance lifetime experiments.
The Co-64 beta-decay feeding levels in the well-studied Ni-64 nucleus were investigated. Whereas the previously known Co-64 decay scheme merely contained 2 gamma rays, the decay scheme established in ...this work contains 18, of which 5 are observed in this work and 6 were previously observed in an (n, gamma) study but not placed in the Ni-64 level scheme. Surprisingly, one additional level-placed at an excitation energy of 3578.7 keV-could be determined. The observed beta-decay paths involve allowed nu f(5/2) -> pi f(7/2) and nu p(1/2) -> pi p(3/2) transitions. Three strongly fed levels around 4 MeV are interpreted to possess possible proton-intruder character.
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