An experimental study of the actinide nucleus 23sU was performed by Coulomb excitation with "*Pb projectiles. The E2-transition matrix elements in the ground state band were measured up to spin 28 by comparing experimental Coulomb excitation yields to semiclassical calculations and by analysing Doppler broadened line shapes measured in coincidence with a gamma-ray sum spectrometer. The E2-metrix elements agree within their errors with the rigid rotor predictions. Neither an increase of the collective transition strength at high spin due to centrifugal stretching as predicted by the Rotation Vibration Model nor a cutoff in collectively as postulated by the Interacting Boson Model is observed. The excitation energies in the ground state band show the presence of an aligned angular momentum of 5h at spin 30 which can be explained by a crossing of an aligned band at hw sz 250 keV. The octupole band shows a constant angular momentum alignment of 3h (above spin 7) and no indication of a bandcrossing.

No abstract

No abstract

Multiple Coulomb excitation measurements on 198"2~176 have been performed with 5 MeV/amu 2~ projectiles and B(E2)-values are determined for transitions between states up to spin 8 +. In t98Hg a reduction of the B(E2)-value for the yrast transition 8+--* 6 + by a factor of 3 as compared to the rigid rotor prediction is observed, which supports the earlier proposed idea that the ground state band is crossed between the 6 + and 8 + state by a weakly interacting viii, 2 rotation aligned band. In each of the two nuclei, 198Hg and 2~176 a state with a possible U=8 + assignment is observed, which is tentatively interpreted as the 8--member of the ground state band.