Abstract
The neutron-rich isotopes of tungsten, osmium and platinum have different shapes in their ground states and present also shape transitions phenomena. Spectroscopic information for these nuclei is scarce and often limited to the gamma rays from the decay of isomeric states. For the neutron-rich even-even osmium isotopes 194 Os and 198 Os, a shape transition between a slightly prolate deformed to an oblate deformed ground state was deduced from the observed level schemes. For the even-even nucleus lying in between, 196 Os, no gamma ray transition is known. In order to elucidate the shape transition and to test the nuclear models describing it, this region was investigated through gamma-ray spectroscopy using the AGATA demonstrator and the large acceptance heavy-ion spectrometer PRISMA at LNL, Italy. A two-nucleon transfer from a 198 Pt target to a stable 82 Se beam was utilized to populate medium-high spin states of 196 Os. The analysis method and preliminary results, including the first life-time measurement of isomeric states with AGATA, are presented.
Highlights
The nuclei with A ≈ 190 between Hf and Pt exhibit a great variety of nuclear phenomena, including Kisomeric states, triaxiality, different shapes in their ground states and shape transitions between them
In the present experiment we used a multi-nucleon transfer reaction together with the large-acceptance magnetic spectrometer PRISMA [1] and the gamma-ray spectrometer AGATA [2, 3] in order to study the nuclear properties in this interesting nuclear region
The beam-like fragments were detected by the PRISMA spectrometer, placed at the grazing angle of the beam-like recoils (57◦)
Summary
The nuclei with A ≈ 190 between Hf and Pt exhibit a great variety of nuclear phenomena, including Kisomeric states, triaxiality, different shapes in their ground states and shape transitions between them. The ground states of the lighter isotopes are prolate deformed. When going to the more neutron-rich isotopes a shape transition occurs and the ground state becomes oblate deformed. The spherical shape is believed to be restored at the N = 126 shell closure. These nuclei are very difficult to populate and the spectroscopic information is rather scarce. Multi-nuclei transfer and fragmentation reactions are the only possible methods to reach such nuclei. In the present experiment we used a multi-nucleon transfer reaction together with the large-acceptance magnetic spectrometer PRISMA [1] and the gamma-ray spectrometer AGATA [2, 3] in order to study the nuclear properties in this interesting nuclear region
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