Nuclear Spins of the IsomersHg191m−185mDetermined by On-Line Quantum-Beat Spectroscopy

The nuclear spins of the very neutron-deficient ${}_{}{}^{191m-185m}{}_{}{}^{}\mathrm{Hg}$ isomers were measured on line at the mass separator ISO LIDE at CERN using pulsed-laser excitation and observation of the time-resolved quantum beats from selected hyperfine-structure states. The spins of these isomers are with $I=\frac{13}{2}$ equal to those of the long-lived isomers ${}_{}{}^{199m-193m}{}_{}{}^{}\mathrm{Hg}$ already known. The persistence of this spin value for eight isomers is explained by the model of rotation-aligned coupling.