Spectroscopy of the long-lived excited state in the neutron-deficient nuclides 195,197,199Po by precision mass measurements.

Direct mass measurements of the low-spin 3/2(-) and high-spin 13/2(+) states in the neutron-deficient isotopes Po-195 and Po-197 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 Po-195,Po-197. Additionally, the excitation energy of isomeric states of lead, radon, and radium isotopes in this region were obtained from alpha-decay chains. These excitation energies complete the knowledge of the energy systematics in the region and confirm that the 13/2(+) states remain isomeric, independent of the number of valence neutrons.