Collective and quasiparticle excitations in superdeformed ¹⁹⁰Hg

Superdeformed (SD) states of ¹⁹⁰Hg have been studied with the Eurogam Phase 2 γ-ray spectrometer using the ¹⁶⁰Gd(³⁴S,4n) reaction. Two new excited SD bands have been found and identified as belonging to this nucleus, bringing the total number of SD bands in ¹⁹⁰Hg to 4. One of the new bands has a dynamic moment of inertia that is very similar to that of the yrast SD band of ¹⁹⁰Hg and most other SD bands in the A∼190 region. In contrast, the other band has a dynamic moment of inertia which is mainly constant as a function of rotational frequency and exhibits a dramatic increase at the lowest frequencies. The observed dynamic moments of inertia are compared with the results of random phase approximation calculations based on the cranked shell model. Finally, the known excited SD band has been extended towards lower frequencies and new transitions have been found linking this band to the yrast SD band. The extracted B(E1) values of the new linking transitions give further support for the possible octupole vibrational character of this band. © 1996 The American Physical Society.