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@PHDTHESIS{Beck:347690,
      author       = {Beck, Sönke Till},
      title        = {{D}irect {M}ass {M}easurements of {N}eutron-{D}eficient
                      {L}anthanides for {N}uclear {S}tructure {S}tudies at the
                      {P}roton {D}ripline},
      school       = {Justus-Liebig-Universität Gießen},
      type         = {Dissertation},
      publisher    = {Universitätsbibliothek Gießen},
      reportid     = {GSI-2023-01108},
      pages        = {138 S.},
      year         = {2023},
      note         = {Dissertation, Justus-Liebig-Universität Gießen, 2023},
      abstract     = {Experimental and theoretical studies of exotic nuclei,
                      i.e., very short-lived nuclei far away from the valley of
                      stability in the chart of nuclides, present a unique and
                      important way to gain general understanding of the atomic
                      nucleus and the governing interactions of its constituents.
                      There is an intriguing interplay of strong, weak, and
                      Coulomb interaction, yet the contributions from all
                      fundamental forces (except gravitation) are integrated in
                      the mass of a nucleus. This makes the mass one of its key
                      properties, allowing to study nuclear structure and basic
                      interactions. Studying exotic nuclei is challenging since
                      they need to be produced first, they are short-lived (many
                      of them have half-lives of only few seconds or even far
                      below), they can only be produced in small quantities, and
                      often the interesting ones are accompanied by a full zoo of
                      other, less exotic and more abundantly produced nuclei.
                      Therefore, powerful separation methods are needed to deal
                      with huge amounts of non-interesting 'by-products' and
                      simultaneously obtain reliable results even for the few
                      nuclei of interest. Moreover, the goal to extract
                      information on basic interactions and nuclear structure
                      requires high accuracies despite low statistics. In this
                      work, improvements and measurements have been implemented
                      and performed at two experiments at different accelerator
                      facilities. In both experiments, a Multiple-Reflection
                      Time-of-Flight Mass-Spectrometer (MR-TOF-MS), which has been
                      build at Gießen University, is used. At the FRS Ion Catcher
                      (FRS-IC) at GSI, Darmstadt, the improvements enabled
                      unprecedented mass accuracies; at TRIUMF’s Ion Trap for
                      Atomic and Nuclear sciences (TITAN) at TRIUMF, Vancouver,
                      Canada, a novel method for mass separation was used to
                      facilitate measurement with previously unknown nuclei.
                      Within these measurements, a new isotope was discovered.
                      This is the first discovery of a new isotope using a
                      time-of-flight mass spectrometer. This demonstrates the
                      advance of the frontier in mass measurements of exotic
                      nuclei and the understanding of nuclear structure at the
                      extremes. At the FRS-IC, several hardware and software
                      elements have been upgraded. The new slow control system at
                      the FRS-IC is running stable and ready to control, monitor
                      and log existing and also various planned extensions of the
                      detector setup. A procedure for systematically tuning the
                      ion optics to unprecedented mass resolving powers R = m/∆m
                      = 1 000 000 and beyond has been established. This enabled
                      the measurement of several exotic nuclei with mass numbers
                      around A = 70 close to the N = Z line. Among these
                      measurements was the first direct mass measurements of
                      69-As, with only 10 events and with reduced uncertainty
                      compared to the average of the previous indirect
                      measurements. For one measued molecule, an accuracy of δm/m
                      = 1.7 × 10e-8 was reached, which is the highest accuracy
                      for MR-TOF-MS world-wide. The techniques applied at the
                      FRS-IC have since been used at the TITAN MR-TOF-MS as well,
                      also there leading to improved mass resolving powers. For
                      TITAN, mass-selective re-trapping was characterized and for
                      the first time used with exotic nuclei, enabling the direct
                      measurement of 2 new and 2 improved ground state masses for
                      neutron deficient Yb isotopes, the first measurement of the
                      excitation energy of the Jπ = 11/2− isomeric state in
                      151-Yb and the indirect determination of 11 more ground
                      state masses connected via α- and p-decays to two of the
                      newly measured masses. The measurement of the mass of 150-Yb
                      is at the same time the first discovery of a new isotope
                      with an MR-TOF-MS. The direct ground state mass measurements
                      of the Yb isotopes and the subsequent determination of
                      masses of Lu isotopes have established the N = 82 neutron
                      shell closure farthest from the valley of β-stability with
                      unmodified shell gap; the shell structure far from the
                      valley of stability is a key question of modern nuclear
                      physics. The measurement of the Jπ = 11/2− isomeric state
                      excitation energy extends a series of constant excitation
                      energies in these odd N = 81 states, which could now be
                      explained by deformation of the ground and isomeric states
                      in collaboration with theorists employing state-of-the-art
                      nuclear mean field.},
      keywords     = {Nuclear Structure (Other) / Proton Dripline (Other) /
                      Lanthanides (Other) / Nuclear Isomers (Other) / Mass
                      Spectrometry (Other) / Mass Separation (Other) /
                      Kernstruktur (Other) / Protonenabbruchkante (Other) /
                      Lanthanoide (Other) / Kernisomere (Other) /
                      Massenspektrometrie (Other) / Massenseparation (Other) /
                      ddc:530 (Other)},
      cin          = {FRS / SuperFRS-EC@FAIR},
      cid          = {I:(DE-Ds200)FRS-20110310OR124 /
                      I:(DE-Ds200)Coll-FAIR-SuperFRS-EC},
      pnm          = {612 - Cosmic Matter in the Laboratory (POF4-612)},
      pid          = {G:(DE-HGF)POF4-612},
      experiment   = {EXP:(DE-Ds200)S474-20200803 / EXP:(DE-Ds200)S459-20200803},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.22029/JLUPUB-18191},
      url          = {https://repository.gsi.de/record/347690},
}