Nuclear structure "southeast" of Pb208: Isomeric states in Hg208 and Tl209

Abstract

The nuclear structure of neutron-rich N>126 nuclei has been investigated following their production via relativistic projectile fragmentation of a E/A=1 GeV U238 beam. Metastable states in the N=128 isotones Hg208 and Tl209 have been identified. Delayed γ-ray transitions are interpreted as arising from the decay of Iπ=(8+) and (17/2+) isomers, respectively. The data allow for the so far most comprehensive verification of the shell-model approach in the region determined by magic numbers Z<82 and N>126. © 2009 The American Physical Society.