Spherical And Deformed Structures In 189Pb

Gamma-ray spectroscopy of high-spin states of the neutron-deficient nucleus 189Pb has been conducted with the 158Gd(36Ar,5n) and 164Er(29Si,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 189Pb. With the second reaction and a pulsed beams, an isomer with a mean life of 32 μsec was found and the decay scheme below it established. Although inconclusive, the available evidence favours identification of the isomer with the (33/2)+ state of the v(i13/2)-3 configuration. The levels observed below the isomer can be identified with states involving three different structures: the neutron (i13/2)-3 multiplet in the spherical well; a prolate-deformed band involving mixed i13/2 neutron orbitals; and a state with the oblate π(2p-2h)0+ x v(i13/2)-1 configuration