SEARCH FOR NUCLEI EXHIBITING THE U(5) DYNAMICAL SYMMETRY

The level energy spectra of a set of 26 nuclei presenting a vibrationa l structure were analysed using a simple U(5) prescription in the IBM- 1 framework. Twelve of these nuclei are relatively well fitted and pre sent level patterns in accordance to the model predictions. They are t hus confirmed or possible U(5) nuclei. The analysis suggests that they present extensive multiphonon structures, This implies the survival o f such structures at higher energies. The experimental B(E2) values be tween multiphonon states are shown to agree with the finite N dependen ce predicted by the IBM. It is also observed that the 2(1)(+) energies are quite generally about 15% lower than expected from the global nuc lear properties.