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Using, for the first time, configuration-constrained potential-energy-surface calculations with the inclusion of β6 deformation, we find remarkable effects of the high order deformation on the high-K isomers in 254 No, the focus of recent spectroscopy experiments on superheavy nuclei. For shapes with multipolarity six, the isomers are more tightly bound and, microscopically, have enhanced deformed shell gaps at N = 152 and Z = 100. The inclusion of β6 deformation significantly improves the description of the very heavy high-K isomers.

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The neutron-rich lead isotopes, up to 216 Pb, have been studied for the first time, exploiting the fragmentation of a primary uranium beam at the FRS-RISING setup at GSI. The observed isomeric states exhibit electromagnetic transition strengths which deviate from state-of-the-art shell-model calculations. It is shown that their complete description demands the introduction of effective three-body interactions and two-body transition operators in the conventional neutron valence space beyond 208 Pb. The shell model is nowadays able to provide a comprehensive view of the atomic nucleus [1]. It is a many-body theoretical framework, successful in explaining various features of the structure of nuclei, based on the definition of a restricted valence space where a suitable Hamiltonian can be diagonalized. This effective interaction originates from realistic two-body nuclear forces based on phenomenological nucleon-nucleon potentials, renormalized to be adapted to the truncated model space. Although the renormalization process can be treated in a rigorous mathematical way, the appearance of effective terms is often neglected in calculations, as a common but incorrect practice. The presence and relevance of these effective forces is well known also in other fields of physics, as for example in condensed matter studies [2]. Indeed, effective three-body terms appear already at the lower perturbation order [3]: PRL 109, 162502 (2012) P H Y S I C A L

Excited states in the N ¼ 102 isotones 166 Gd and 164 Sm have been observed following isomeric decay for the first time at RIBF, RIKEN. The half-lives of the isomeric states have been measured to be 950(60) and 600(140) ns for 166 Gd and 164 Sm, respectively. Based on the decay patterns and potential energy surface calculations, including β 6 deformation, a spin and parity of 6 − has been assigned to the isomeric states in both nuclei. Collective observables are discussed in light of the systematics of the region, giving insight into nuclear shape evolution. The decrease in the ground-band energies of 166 Gd and 164 Sm (N ¼ 102) compared to 164 Gd and 162 Sm (N ¼ 100), respectively, presents evidence for the predicted deformed shell closure at N ¼ 100. In the exploration of the nuclear landscape, it is evident that the neutron-rich side of stability contains a vast unknown territory, where approximately half of all the bound nuclides remain to be identified. Furthermore, this is the domain of rapid-neutron-capture (r process) nucleosynthesis, which is poorly understood and yet is key to the creation of chemical elements from iron to uranium (Z ¼ 26-92) in stellar environments [1]. With the advent of the current generation of radioactive-beam facilities, it is now possible to address some of the open questions PRL 113, 262502 (2014) P H Y S I C A L

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The low-lying states in 106 Zr and 108 Zr have been investigated by means of β-γ and isomer spectroscopy at the RI beam factory, respectively. A new isomer with a half-life of 620 ± 150 ns has been identified in 108 Zr. For the sequence of even-even Zr isotopes, the excitation energies of the first 2 + states reach a minimum at N = 64 and gradually increase as the neutron number increases up to N = 68, suggesting a deformed sub-shell closure at N = 64. The deformed ground state of 108 Zr indicates that a spherical sub-shell gap predicted at N = 70 is not large enough to change the ground state of 108 Zr to the spherical shape. The possibility of a tetrahedral shape isomer in 108 Zr is also discussed.