Description of high spin states

Abstract

In this talk mainly three points will be discussed: (i) The nature of the second backbending (bb) in the rare earth nuclei will be theoretically investigated. It will be confirmed that 2. bb is due to the alignment of a h11/2 -proton pair. The oscillating behaviour of the 2. bb can explain the variation of the second anomaly in the N=90 isotones. Strong variations of the 2. bb with the neutron number can be explained by the change of the deformation s. (ii) The smooth increase of the moment of inertia in the actinide nuclei is explained mainly by the alignment of a i13/2 proton pair. This is confirmed by measurements of the g-factors and the blocking effect in odd proton nuclei where the odd proton is in a i13/2 level. In 248Cm, where one has a smaller deformation, one finds a roughly equal role for i13/2 and j15/2 neutrons for the increase of the moment of inertia. (iii) In this third part we study high spin spectra in the even mass Hg-isotopes by coupling two quasi-particles to an interacting boson core. This calculation can reproduce the anomalous behaviour of the yrast states around angular momentum 8, 10 and 12. The agreement for the yrast state is similar in an earlier calculation where two quasi-particles have been coupled to an asymmetric rotor. The g-factors of these states measured in Bonn and the reduced quadrupole transition probabilities are also nicely reproduced in both models.