%0 Thesis
%A Kaleja, Oliver
%T High-precision mass spectrometry of nobelium, lawrencium and rutherfordium isotopes and studies of long-lived isomers with SHIPTRAP
%I Johannes-Gutenberg Universität Mainz
%V Dissertation
%M GSI-2020-01337
%P 147 p.
%D 2020
%Z Dissertation, Johannes-Gutenberg Universität Mainz, 2020
%X In this work, the first successful application of the recently developed Phase-Imaging Ion-Cyclotron Res-onance (PI-ICR) technique in the region of the heaviest elements is presented. For the first time, theatomic masses of several nobelium (No,Z= 102), lawrencium (Lr,Z= 103) and rutherfordium (Rf,Z= 104) isotopes and isomers have been measured directly, reaching uncertainties on the order of fewkeV/c2using the Penning-trap mass spectrometer SHIPTRAP. These heavy radionuclides were producedin fusion-evaporation reactions and separated from the primary beam by the velocity filter SHIP locatedat the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany. The mass measurementswere carried out at production rates of few ions per second down to few ions per minute. To improvethe overall efficiency on stopped and thermalized ions, the recently developed cryogenic gas-stopping cellwas implemented into the existing beam line. Its performance with respect to purity and efficiency hasbeen characterized and improved. The overall efficiency of SHIPTRAP is increased by about one orderof magnitude with respect to previous measurements on heavy ions. The atomic masses are determinedby measuring the cyclotron frequency of the ion of interest in the strong magnetic field of a 7 T super-conducting magnet. The atomic masses of251No,254Lr and257Rf were measured directly for the firsttime, reaching high precision. The latter marks the very first direct high-precision mass spectrometry of asuperheavy element with a detection rate of one detected ion per day and only five ions in total. In addi-tion, the uncertainties of the atomic masses of254No and255,256Lr have been reduced by up to two ordersof magnitude with respect to previous experiments at SHIPTRAP. The precise determination of bindingenergies is key in nuclear physics as it is a model-independent quantity comprising all interactions that arepresent within the atomic nucleus. This allows studying, e.g., quantum-mechanical shell effects, which areelementary for the existence of (super-)heavy elements. The results of this work are used to benchmarkatomic mass models in the vicinity of the deformed neutron shell closure atN= 152. Furthermore, thesemeasurements will provide additional anchor points of very heavy odd-Nand odd-Zas well as odd-Anuclides, affecting the masses up to darmstadtium (Z= 110). With the enhanced mass resolving powerof up to 11 000 000, the isomeric states251mNo,254mLr and255mLr were resolved from their respectiveground states despite low excitation energies of tens of keV. Their masses and the corresponding excitationenergies were measured directly for the first time. Up to now, only tentative level energies were derivedfrom previousα-decay spectroscopy experiments. This work proves the feasibility of PI-ICR in the regionof the heaviest elements at lowest yields and particle integrals. It paves the way to precisely study exoticsuperheavy species with very long half-lives which becomes inevitable when progressing towards the islandof stability.
%F PUB:(DE-HGF)11
%9 Dissertation / PhD Thesis
%R 10.25358/OPENSCIENCE-5111
%U https://repository.gsi.de/record/236616