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Dipole collectivity in S YRa

Thesis/Dissertation ·
OSTI ID:6220704
While cluster models have had by far their greatest use, apart from natural radioactivity, in light nuclei in the region from YBe to UCa, Iachello and Jackson recently suggested that even in heavy nuclei, just above closed shells, four valence nucleons could form a valence alpha particle cluster orbiting the remaining core. In heavy nuclei, as opposed to light, reflecting the neutron excess (N > Z), such cluster separation results in a separation of the centers of charge and mass and thus generate a static electric dipole moment. The author has undertaken a detailed experimental study of this question using a wide range of techniques and focussing upon the S YRa nucleus. Using a SYPb target and a TC beam at Yale and the reverse reaction at GSI, the author has identified the quadrupole and dipole band members in the level spectrum of this nucleus. From measurements of the absolute lifetimes of many states ranging up to that having J = 15h, the author has shown that the electromagnetic deexcitation matrix elements are indeed enhanced and that they exhaust as much as 15% of molecular sum rule appropriate for these cluster configurations. Having measured many of the pertinent parameters, the author has shown that the Iachello-Jackson dipole model can reproduce what the author has found in S YRa. The new data also provides a stringent test of the spectrum generating algebraic and other approaches to this understanding.
Research Organization:
Yale Univ., New Haven, CT (USA)
OSTI ID:
6220704
Country of Publication:
United States
Language:
English