| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1999: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1998: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
Nucleus is a finite quantal system and there observed many phenomena, which can be understand by an interplay between the collective and independent degrees of freedoms. Especially interesting phenomena are those observed recently at high-spin and highly excited extreme states. In this research we have studied various kinds of such phenomena related to the "phase-transitions" or "phase-coexistences"caused by the nuclear-shape and rotation degrees of freedoms by using a simple tunneling model.
The first one is the decay-out of superdeformed rotational bands. This phenomenon is a transition of extremely deformed states to normally deformed states. Performing systematic calculations, we have found that the potential energy surfaces are considerably different in various observed regions of superdeformed bands. Furthermore, we have extended the previously invented tunneling model to excited states, and have successfully reproduced the number of excited superdeformed bands by including the ef
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fect ofdecay-out.
The second research is the tunneling in the tilting-angle degrees of freedom of rotaitonal axis. It has been observed that the high-spin isomers, which are rotating around the symmetry-axis, decay to the yrast rotational bands, which are rotating around axis perpendicular to the symmetry-axis. Such decays can be understood as transitions either in the triaxial-deformation degrees or in the tilting-angle degrees of freedoms. We have successfully developed a method to calculate the potential energy surface with respect to these degrees of freedoms, and been studying two degrees of freedoms on the same footing.
Finally, we have also investigated the nucleon effective mass, which is important to study the high-spin and highly excited extreme states, taking into account of the coupling effects of collective shape degrees of freedoms. We have found that the coupling effects reduces very much at high-spin limits, and it causes an important change to, for example, the nuclear level-density. Less
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