Rare-earth (RE) isotopes in the vicinity of the double mid-shell at Z = 66 and N = 104 are exemplary cases of well-deformed nuclei in which the energy levels are characterized by collective rotations and surface vibrations, as well as by quasi-particle excitations. The presence of these excitation modes within a narrow range of energy causes interplay among them to a greater or lesser extent, giving rise to a rich variety of structural aspects in deformed nuclei. Besides their importance for nuclear structure study, the decay and deformation properties of neutron-rich RE isotopes are suggested to play a crucial role in the formation of the so-called RE-element peak around A = 165 in the r-process solar abundance distribution.
Despite such a broad range of interest, spectroscopic information still remains scarce due to the experimental difficulties in producing neutron-rich nuclei around and beyond the double mid-shell. The advent of the third-generation in-flight fragment separator facility, the RI-Beam Factory (RIBF) at RIKEN, enables access to this exotic area and allows for systematic studies of their decay properties . In this seminar, I will present the results of β-decay half-lives  and β-γ/isomeric-decay spectroscopy  of neutron-rich RE isotopes obtained as part of the EURICA (EUROBALL-RIKEN Cluster Array) project at RIBF, along with a discussion about their impact on nuclear structure and nuclear astrophysics.
 T. Nakamura, H. Sakurai, and H. Watanabe, Prog. Part. Nucl. Phys. (in press).
 J. Wu et al., Phys. Rev. Lett. 118, 072701 (2017).
 H. Watanabe et al., Phys. Lett. B 760, 641 (2016).
* The presentation file is written in English, but the talk will be given in Japanese.
７月２６日、13:00 - 14:00, 14:30-15:30。場所はセミナー会場です。対象は学部・修士以上。
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