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Abstract

This cumulative dissertation comprises ISOLTRAP's transition from the well-established
Penning-trap mass spectrometry (PTMS) technique, ToF-ICR, to the next-generation
PTMS technique, called PI-ICR. First, the highest precision ever achieved at
the ISOLTRAP experiment using ToF-ICR allowed for a reduction of the Q_EC-value uncertainty
of the ²¹Na → ²¹Ne and ²³Mg → ²³Na electron-capture decays by a factor of five
compared to their literature values. Within these findings, the most precise ℱt-values
and, in the case of ²¹Na → ²¹Ne, a new Vud-element value of the CKM quark-mixing
matrix were derived and found to agree with the standard model of particle physics.
Second, ISOLTRAP's first publication using PI-ICR demonstrated a supreme relative
mass precision of δm/m = 1.4×10^-9 in only 4 hours experiment time. The result reduced
the uncertainty on the Q_EC-value of the ¹³¹Cs → ¹³¹Xe decay by a factor of 25 and
consequently precluded the decay as a possible candidate for a direct neutrino-mass
determination. Third, ultra-high mass resolving powers exceeding 10⁶ using PI-ICR
allowed for the first spatial resolution of isomeric states in neutron-rich cadmium isotopes.
Thus, this publication presented the first experimental data describing the
N = 82 neutron-shell closure below the proton-magic Z = 50 while implying a drastic
weakening of the N = 82 shell. Furthermore, these measurements allowed for sophisticated
comparison with state-of-the-art nuclear-theoretical models.