Two-quasiparticle $K^{\pi }{=8\mathrm{}}^{-}$ isomeric states in the $A\sim 130$ and 180 regions are studied with configuration-constrained calculations of potential-energy surfaces. Strong shape-polarization effects due to the two quasiparticles are found. In particular, the nuclei ${}^{188}\mathrm{Pb}{,}^{186}\mathrm{Hg},$ and ${}^{126}\mathrm{Te}$ can be polarized from ground-state spherical or oblate shapes to prolate shapes, indicating a combination of K isomerism and shape isomerism as the Fermi level approaches shell closure.

• Received 12 October 1998

DOI:https://doi.org/10.1103/PhysRevC.59.731