A dipole band above the Iπ= 31/2− isomeric state in 189Pb

Abstract

This contribution focuses on the new observation of a dipole band built upon an Iπ=31/2− isomeric state in 189Pb, identified using recoil-isomer tagging at the University of Jyväskylä, Finland. This is the lightest odd-mass Pb isotope in which a dipole band is known. By comparison with the heavier-mass dipole bands, the dipole band in 189Pb was deduced to be based upon a π(s1/2−2h9/2i13/2)11−⊗v(i13/2−1)13/2+$\pi {\left( {s_{1/2}^{ - 2}{h_{9/2}}{i_{13/2}}} \right)_{{{11}^ - }}} \otimes v{\left( {i_{13/2}^{ - 1}} \right)_{13/{2^ + }}}$ configuration. However, in the 189Pb dipole band, the initial aligned angular momentum was larger than that exhibited by the dipole bands in the heavier-mass isotopes. This may be evidence for a reduced repulsive proton/neutron-hole interaction in 189Pb.