Direct mass measurements of the low-spin $3/2^{ (-)}$ and high-spin $13/2^{ (+)}$ states in the neutron-deficient isotopes $^{ 195}$Po, $^{ 197}$Po, and high-spin $13/2^{ (+)}$ state in $^{ 199}$Po were performed with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE-CERN. These measurements allow the determination of the excitation energy of the isomeric state arising from the $\nu$i$_{ 13/2}$ orbital in $^{ 195,197}$Po. Additionally, the excitation energy of isomeric states of lead, radon, and radium isotopes in this region were obtained from $\alpha$-decay chains. The new excitation energies complete the knowledge of the energy systematics in the region and confirm for the first time that the $13/2^{ (+)}$ states remain isomeric, independent of the number of valence neutrons.
Categories: nucl-ex
