Two new rotational bands of distinct character have been identified in ${}^{164}\mathrm{Hf}$. They are suggested to correspond to the long-anticipated triaxial strongly deformed (TSD) bands predicted by theoretical studies. The bands have been linked to known states, and the level spins and energies could be determined. The bands are also substantially stronger in intensity and are located at lower spins than the previously observed TSD bands in ${}^{168}\mathrm{Hf}$, hereby making ${}^{164}\mathrm{Hf}$ the best even-even system so far for the study of TSD structures in the $A\sim 160$ mass region. Cranking calculations based on the modified-oscillator model suggest that the bands are associated with four-quasiparticle configurations that involve high-$j$ intruder ${\left(i_{13/2}\right)}^2$ proton orbitals.

• Received 14 August 2013

DOI:https://doi.org/10.1103/PhysRevC.88.041306