New μs isomers in the neutron-rich ²¹⁰Hg nucleus

Abstract

Neutron-rich nuclei in the lead region, beyond $N=126$, have been studied at the FRS-RISING setup at GSI, exploiting the fragmentation of a primary uranium beam. Two isomeric states have been identified in ²¹⁰Hg: the $8^{+}$ isomer expected from the seniority scheme in the $\nu g_{9/2}$ shell and a second one at low spin and low excitation energy. The decay strength of the $8^{+}$ isomer confirms the need of effective three-body forces in the case of neutron-rich lead isotopes. The other unexpected low-lying isomer has been tentatively assigned as a $3^{-}$ state, although this is in contrast with theoretical expectations.