Mass Measurements of Exotic Ions in the Heavy Mass Region for Nuclear Structure Studies at ISOLTRAP

The mass is a unique fingerprint of each nucleus as it reflects the sum of all interactions within it. Comparing experimental mass values with theoretical calculations provides an important benchmark of how well the role of these interactions is already understood. By investigating differences of experimental binding energies, such as two-neutron separation energies (S2n), valuable indications for nuclear-structure studies are provided. The present thesis contributes to these studies providing new high-precision mass measurements especially in the heavy-mass region. Here, nuclear theory is heavily challenged due to the large number of nucleons. The data have been obtained at the Penning-trap mass spectrometer ISOLTRAP located at the radioactive-ion-beam facility Isolde at CERN. For the determination of the masses, the time-of-flight ion-cyclotron-resonance technique has been applied. While the new mass data for 122−124Ag continue existing trends in the S2n energies, the new mass values for 207,208Fr render them more precisely. In the case of the mass values for 184,186,190,193−195Tl a new interesting odd-even effect has been revealed. The comparison of the measured mass values with theoretical models furthermore demonstrates significant problems in reproducing the strength of the pairing correctly. This is of special interest for the discussion about shape coexistence in the region around the doubly-magic 208Pb