Microscopic Properties of Superdeformed Nuclei

Sammanfattning: Many high spin rotational bands in superdeformed nuclei have been found in the A ~ 140-150 region, but so far no linking transitions to known normal-deformed states have been found in these nuclei. Therefore, configuration and spin assignments have to be based on indirect spectroscopic information. Identical bands were first discovered in this region of superdeformed shapes. At present, some identical bands have also been found at normal deformation, but such bands are more common at superdeformation. Recently lifetime measurements have given relative quadrupole moments with high accuracy. Spectroscopic quantities are calculated using the configuration constrained cranked Nilsson-Strutinsky model with the modified oscillator potential. In a statistical study the occurrence of identical bands is tested. Comparing superdeformed and normal deformed nuclei, the higher possibility for identical bands at superdeformation is understood from calculated reduced widths of the Egamma and J(2) distributions. The importance of high-N orbitals for identical bands is also discussed. Additivity of electric quadrupole moment contributions in the superdeformed A ~ 150 region is discussed with the nucleus 152Dy as a core. In analytic harmonic oscillator calculations, the effective electric quadrupole moment qeff, i.e. the change in the total quadrupole moment caused by the added particle, is expressed as a simple function of the single-particle mass quadrupole moment qv. Also in realistic calculations, simple relations between qeff and qv can be used to estimate the total electric quadrupole moment, e.g. for the nucleus 142Sm, by adding the effect of 10 holes, to the total electric quadrupole moment of 152Dy. Furthermore, tools are given for estimating the quadrupole moment for possible configurations in the superdeformed A ~ 150 region. For the superdeformed region around 143Eu, configuration and spin assignments are made based on effective alignments. The region is connected to, and compared with, previously investigated 146-153Gd nuclei. The two regions show similarities but it appears difficult to get consistent alignments in the whole region around 143Eu.