G Factor of the High-Spin Isomer in 149DY and Large Oblate Deformation Induced by Collapse of the N = 82 Core

The g factor of the high-spin isomer in ¹⁴⁹Dy (t_1/2 = 28 ns) has been measured using the γ-ray time-differential perturbed angular distribution (TDPAD) technique with a pulsed beam of ¹³²Xe. The experimental result indicates a main configuration of the isomer to be [π (h² _11/2) ⊗ ν (f_7/2 h_9/2 i_13/2 (d^-2 _3/2; )₀ ; ) ; ]_49/2+ . A deformed independent particle model (DIPM) calculation predicts that a large oblate deformation is caused by breakdown of the N = 82 shell-closure at this isomeric state.