The high-spin rotational bands in ${}^{168}$Hf and the triaxial bands in Lu nuclei are analyzed using the configuration-constrained cranked Nilsson-Strutinsky (CNS) model. Special attention is given to the up-sloping extruder orbitals. The relative alignment between the bands which appear to correspond to triaxial shape is also considered, including the yrast ultrahigh-spin band in ${}^{158}$Er. This comparison suggests that the latter band is formed from rotation around the intermediate axis. In addition, the standard approximations of the CNS approach are investigated, indicating that the errors which are introduced by the neglect of off-shell matrix elements and the cutoff at nine oscillator shells (${\mathcal{N}}_{\max }=8$) are essentially negligible compared to other uncertainties. On the other hand, the full inclusion of the hexadecapole degree of freedom is more significant; for example it leads to a decrease of the total energy of $\sim 500$ keV in the triaxial superdeformed (TSD) region of ${}^{168}$Hf.

• Received 27 August 2011

DOI:https://doi.org/10.1103/PhysRevC.86.014309