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Abstract

The high-precision Penning-trap mass spectrometer Pentatrap was designed to perform
mass-ratio measurements of highly charged ions with relative uncertainties of 10⁻¹¹. The
unique features of the Pentatrap experiment are the external ion sources providing
highly charged ions, the detection systems with single-ion sensitivity and especially the
stack of five Penning traps, which allows simultaneous measurements of single ions in
the traps. In the scope of this thesis, the first high-precision mass measurements with a
relative precision partially below δm/m ≈ 10⁻¹¹ were performed. As a first benchmark
test, the mass differences of five xenon isotope pairs were determined. Comparison to
the literature values led to an improvement of the uncertainty of the mass differences of
a factor between 4 and 1700, in agreement with literature. In order to demonstrate the
accuracy of Pentatrap, the binding energy of the 37^th electron in ¹³²Xe was determined
as a proof-of-principle measurement by determining the mass difference of ¹³²Xe¹⁷⁺ and
¹³²Xe¹⁸⁺. The agreement of the result with theory allows performing stringent tests of
quantum electrodynamics using binding energies in ions with an even higher charge state
in the future. Lastly, the discovery of metastable electronic states in highly charged rhenium
and osmium ions by mass difference measurements, confirmed by theory, extends
the applicability of Penning-trap mass spectrometry to tests of atomic structure theories
and to the identification of long-lived excited states for a possible new generation of clocks
using highly charged ions.