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Resonance ionization enables the production of isobarically pure ion beams through multi-step resonant laser excitation, exploiting the unique shell structure of the different elements. Due to the suppression of unwanted neighboring elements in the ionization process as well as the high efficiency, this type of ion source is preferably used for the ionization of short-lived radionuclides in on-line facilities such as ISOLDE/CERN.

The working group LARISSA is working on the development and optimization of laser ion sources in combination with high repetition solid state laser systems. The method has already been fully characterized for a variety of chemical elements and an efficient ionization could be demonstrated.

The goal of this work is the further optimization of the laser ion source with respect to the achievable ion current. Therefore the existing pulsed Ti:sapphire laser system will be operated with higher repetition rates. The work includes the characterization of the laser system and measurements of the efficiency of the laser ion source at different laser repetition rates and ion currents.

Partial aspects of this project can also be assigned as bachelor thesis.

For the exact determination of the half-life of molybdenum-93, which is approximately 4000 years, the branching ratio of radioactive decay needs to be measured. This can be done by measuring the ratio of the daughter nuclei niobium-93 and niobium-93m. Since these are isomers with nearly the same mass, this ratio cannot be measured by means of mass spectrometry alone.

With the help of selective laser excitation, however, differences in the hyperfine structure of the two nuclei, caused by different magnetic moments, can be exploited to achieve a separation by laser ionization.

The aim of this work is to characterize suitable atomic transitions for such a separation and to quantify the sensitivity and spectral resolution on stable niobium-93, followed by a measurement of the isotope ratio Nb-93/Nb-93m by laser spectroscopy. For the first time the magnetic moment of Nb-93m (as well as other radioactive Nb nuclides) can be determined by measuring the hyperfine structure.

Partial aspects of this project can be assigned as bachelor thesis.