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The available data on levels in 98 Y have been reevaluated and interpreted using recently published information on band structure in this region. A calculation in the interacting boson model framework suggests that the 1182 keV 0.8 s isomer is a spherical 10 − state with the g 9/2 h 11/2 configuration. This assignment implies that the 8.0 s bandhead at 496 keV is a I =4 − state, with the highly probable ͓422͔5/2 ͓541͔3/2 configuration. The level structure of 98 Y is well reproduced by coupling the levels of its both spherical and deformed odd-A neighbors and the origin of the isomeric states is understood.

A band with a rotational pattern based on a state at 585.1 keV has been identified in the N= 59 neutron-rich nucleus 97St. Its properties lead to the [422] 3/2 Nilssonorbital assignment for the band head. There is evidence for a second band with the head at 644.7 keV and the configuration [-541] 3/2. Since the ground state and the lowest excited levels are spherical, shape coexistence is established for 97Sr. A deformed nature of several levels at 500-600 keV results also from QRPA-model calculations. The structure of the low-lying spherical levels has been studied in the frame of the IBF model. The results of the present investigations lead to a better understanding of the N= 59 isotones which constitute the link between the spherical and deformed nuclei at A ~ 100 as a species with shape coexistence but without any indications of particular softness.

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This work presents the production and extraction of the short-lived radionuclide 6 He in yet unmatched yields from the ISOLDE facility at CERN. It is the first report of 6 He production using spallation neutrons via the 9 Be(n, α) 6 He reaction. These neutrons are produced from the 1.4 GeV proton beam of the Proton Synchrotron Booster (PSB) striking a tungsten converter, and are impinging on a porous BeO material. The central position of 6 He in future experiments is due to its role as a necessary radioactive nucleus to realize the β-beam at CERN, a next-generation facility to study neutrino oscillation parameters, and hence neutrino masses. In the β-beam scenario, an intense beam of radioactive 6 He nuclei will be produced, accelerated to multi-GeV energies and stored in a dedicated storage ring. The resulting virtually mono-directional anti-neutrino beam from the decay of the stored 6 He nuclei will be directed towards a remote underground neutrino detector. A similar beam of, e.g., 18 Ne will provide neutrinos, an ideal concept to test CP violation in the neutrino sector. The results of the present experiment demonstrate for the first time that the necessary conditions for the realization of the proposed β-beam scheme with anti-neutrinos can be fulfilled.

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