γ-ray spectroscopy of high-spin states of the neutron-deficient nucleus ${}^{189}\mathrm{Pb}$ has been conducted with the ${}^{158}\mathrm{Gd}({}^{36}\mathrm{Ar},5n)$ and ${}^{164}\mathrm{Er}({}^{29}\mathrm{Si},4n)$ reactions. With the first of these, detection of evaporation residues and mass gating were used to unambiguously assign a number of prompt γ-ray transitions to ${}^{189}\mathrm{Pb}$. With the second reaction and a pulsed beam, an isomer with a mean life of 32 μs was found. Although inconclusive, the available evidence favors identification of the isomer with the ${\frac{33}{2}}^{+}$ state of the $\nu (i_{13/2}){}^{-3}$ configuration. The levels observed below the isomer can be identified with states involving three different structures: the neutron $(i_{13/2}){}^{-3}$ multiplet in the spherical well; a prolate-deformed band involving mixed $i_{13/2}$ neutron orbitals; and a state with the oblate $\pi (2p\text{−}2h){}_{0^{+}}\otimes \nu (i_{13/2}){}^{-1}$ configuration. The evidence for structures associated with different shapes is supported by the observation of $E0$ components in some of the $J^{\pi }\to J^{\pi }$ transitions linking them.

• Received 2 January 2005

DOI:https://doi.org/10.1103/PhysRevC.71.054302