Well-Deformed Oblate K Isomers Induced by Oblate Intruder States

With configuration-constrained potential energy surfaces, it has been found that the neutron-deficient Z≈82 nuclei can have well-deformed oblate K isomers which are formed by exciting quasiparticles to the proton i_13/2 and h_9/2 oblate intruder orbitals. To achieve the configuration-constrained calculations, the maximum-overlap method of wavefunctions is proposed. In the present calculations of quasiparticle states, quadrupole pairings are included. The observed K^π = 11^- isomer in ¹⁸⁸Pb is confirmed to be oblately deformed, with energy consistent with the experiment. Some low-lying oblate isomeric states are predicted for ¹⁸⁷Tl.