Study of the long-lived excited state in the neutron deficient nuclides ${}^{195,197,199}$Po by precision mass measurement

Abstract

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 $\hat{I}½$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 $\hat{I}\pm$-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.