New Aspects of Nuclear Deformation

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In this research project, nuclear quadruple and octupole deformations have been studied from various new aspects, including both dynamical and static deformations. The theoretical tool we have used is the Interacting Boson Model (IBM). The gamma-unstable deformation is known for Xe and Ba nuclei with the mass number-130. We studied the structure of ^<130>Xe, in particular, in order to investigate to what extent the O(6) dynamical symmetry holds in this nucleus. The data taken by Koeln group indicates very clearly the O(6) dynamical symmetry properties. The O(6) dynamical symmetry is a perfect description, but appears to be rather abstract. Otsuka developed a new interpretation of its structure. The O(6) dynamical symmetry can be viewed as the phonon excitation from a deformed equilibrium. With this view, a more intuitive understanding of the structure of gamma-unstable nuclei can be obtained. The quantum chaos has been studied in terms of the rotational damping and the width. The magnetic transitions are enhanced anomalously in the O(6) nuclei, and data taken recently by the Koeln group have been analyzed. The Interacting Boson-Fermion Model - 2 has been used to analyze the Ml excitation data by the Koeln group for odd-A nuclei. The nuclei ^<125,127>Xe have been studied in terms of the Interacting Boson-Fermion Model - 2, and a good agreement between experiment and calculation has been obtained.