High-spin states in the ${}_{68}^{164}$Er${}_{96}$ region were studied using ${}^9$Be $+$ ${}^{160}$Gd reactions. Pulsed beam conditions were exploited for enhanced sensitivity to delayed $\gamma$-ray transitions. New isomers were identified in ${}^{161}$Dy, ${}^{163}$Ho, ${}^{162}$Er, and ${}^{165}$Er. The ${}^{162}$Er isomer is interpreted to decay by $E1$ transitions to the ground-state band with a reduced hindrance of $f_{\nu }=33$. A plot of $f_{\nu }$ values for all $\Delta K=7$, $E1$ transitions from two-quasiparticle isomers to the ground-state bands of even-even nuclei reveals only a small influence from the dynamic to kinematic moment-of-inertia ratio, which provides a measure of Coriolis $K$ mixing within the ground-state band. This is interpreted to imply that the relatively low hindrances are due to $K$ mixing in the isomer, caused by a combination of Coriolis and octupole band mixing.

• Received 14 December 2011

DOI:https://doi.org/10.1103/PhysRevC.85.024313