A dipole band above theIπ= 31/2−isomeric state in189Pb

D M Cullen

doi:10.1051/epjconf/201612302001

Abstract

This contribution focuses on the new observation of a dipole band built upon an I π =31/2− isomeric state in 189 Pb, identified using recoil-isomer tagging at the University of Jyvaskyla, 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 189 Pb was deduced to be based upon a configuration. However, in the 189 Pb 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 189 Pb.

Highlights

Dipole bands are a common feature of the neutrondeficient odd-mass Pb isotopes [1,2,3,4,5,6,7,8]
Several prompt-delayed matrices were constructed for events which were separated in time by up to 60 μs (∼3 half-lives of the 189Pb isomeric state)
By gating on the known [9, 11] delayed gamma rays in 189Pb, six new prompt transitions of energies 206, 335, 389, 413, 419- and 435-keV were established to lie above the 32 μs proposed dipole band-head state in 189Pb

Summary

Introduction

Dipole bands are a common feature of the neutrondeficient odd-mass Pb isotopes [1,2,3,4,5,6,7,8] These bands exhibit a structure which resembles a strongly-coupled rotational band, the nuclear shape is approximately spherical and the strongly-coupled structure has strong M1- and weak E2-transitions. Dipole bands in this region are known to originate from the coupling of protons in the h9/2 orbital to neutron holes in the i13/2 orbital [8,9,10]. The present contribution describes the results of a new experiment which was performed at the University of Jyväskylä to establish the transitions which were built up on this isomeric state

Experiment

Results

Discussion