High-spin properties ofEr164in the multiple band crossing region

High-spin states in ${}_{}{}^{164}{}_{}{}^{}\mathrm{Er}$ have been studied by using the ${}_{}{}^{150}{}_{}{}^{}\mathrm{Nd}$(${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$,$4n\gamma$) and ${}_{}{}^{164}{}_{}{}^{}\mathrm{Dy}$($\alpha$,$4n\gamma$) reactions and by multiple Coulomb excitation with ${}_{}{}^{136}{}_{}{}^{}\mathrm{Xe}$ ions. Several positive-parity bands are excited, and two negative-parity bands have been identified. The previously reported backbending behavior of the yrast sequence is demonstrated to result from the intersection of the ground band (seen to spin ${22}^{+}$) with an even-spin "superband" observed from spins ${12}^{+}$ to ${24}^{+}$. The odd-spin yrast superband and the second lowest even-spin superband also have been observed. All the superbands have moments of inertia appreciably larger than the ground band. The observed intersection of these multiple superbands with the $\gamma$ band produces different backbending behavior and a staggering of the energies of the odd- and even-spin members of the $\gamma$ band. $B\left(E2\right)$ values for transitions below and through the band intersection regions of both the ground band and $\gamma$ bands have been deduced from multiple Coulomb excitation yields. In addition, lifetimes have been measured for the ground band by the Doppler-broadened line-shape technique. The level energies and $B\left(E2\right)$ values are consistent with weak interaction matrix elements (≈ 45 keV) between the intersecting bands. The $B\left(E2\right)$ values of the unperturbed band are found to obey the simple rigid-rotor relationship. The $7^{-}$ negative-parity band exhibits a normal rotational sequence, while the $5^{-}$ band exhibits a large odd-even staggering and a larger moment of inertia. Two-quasiparticle-plus-rotor model calculations indicate strong rotation-alignment and reproduce the observed properties of the high-spin states for both the positive- and negative-parity bands in ${}_{}{}^{164}{}_{}{}^{}\mathrm{Er}$.