Doctors defense of Felix Weber in 2023

On 28 Mar Felix Weber finished her PhD thesis titled

Towards Z=100 laser spectroscopy on atomic and nuclear structure in californium and einsteinium in the LARISSA group.

His thesis deals with laser spectroscopic investigations on the atomic and nuclear structure of the (on earth) purely artificially produced actinide elements californium (Z = 98) and einsteinium (Z = 99).

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Doctoral defense of Nina Kneip in 2022

On Oct 26, 2022, Nina Kneip finished her PhD thesis titled Resonance ionization mass spectrometry: Isotope enrichment of rare species and spectroscopy in actinides for ultra-trace analysis in the LARISSA group.

Her thesis focuses on the three prominent application areas of RIMS, i.e. the implantation of pure isotopes, ultra-trace analysis of rare radiotoxic isotopes and, finally, spectroscopic investigations of atomic and nuclear properties, in this work carried out on the five actinide elements uranium, neptunium, plutonium, americium and curium.

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Klaus Wendt awarded with the Robert-Wichard-Pohl-Award

The Robert-Wichard-Pohl-Award 2022, granted by the German Physical Society, goes to Klaus Wendt

"For his outstanding work in the field of atomic and nuclear physics and trace analysis, as well as for the development of laser systems that are now in use worldwide. In addition, with his engaging personality and enormous commitment, Klaus Wendt has inspired students and the public for physics and developed new concepts for the education of teachers and students."

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Applied Photonics Bad Honnef Physics School Poster Award

Poster award handed over by Prof. Dr. Neu.
Poster award handed over by Prof. Dr. Neu.

The Applied Photonics Bad Honnef Physics School, sponsored by the Wilhelm and Else Heraeus Foundation, specializes on advanced research topics in photonics. This time the focus was on photonics systems and application areas of laser technology in the industrial and scientific contexts, which were addressed in lectures and discussed through poster presentations by participants.

Nina Kneip presented her work on Laser spectroscopy and ultra-trace analysis on lighter actinides – from Uranium to Curium, and won the poster award sponsored by Zeiss

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Innovative Training Network LISA launched

The international collaboration LISA (Laser Ionization and Spectroscopy of Actinide Elements), an Innovative Training Network including partners from all over the globe, started in early 2020. The project funds 15 early stage researchers over a period of 4 years. Read more

For the LARISSA group, Magdalena Kaja started her PhD project in October 2020.

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Missing atomic energy levels of Actinium detected

Generation of the 1337 nm wavelength by difference frequency mixing of 457 nm and 700 nm laser light.

The lowest-lying odd-parity energy levels of the atomic system of actinium have been predicted by theory for a long time, but were never experimentally observed. A team of scientists from the group of Prof. Budker at HIM and the LARISSA group finally revealed these "missing" lines in a laser spectroscopic experiment.

The extracted properties of the atomic transitions were compared to state-of-the-art atomic structure calculations and were found to be in perfect agreement. The collaboration of experimenalists and theorists from China, Germany, USA and Russia published the results in Physical Review Letters.

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Fundamental property of Earth’s rarest element measured


An international team of researchers succeeded in the measurement of the electron affinity of the all radioactive element astatine. The results are published in Nature communications.

The isotope 211At is a perfect candidate for targeted alpha therapy. The measured values of the electron affinity and the earlier measured ionization potential provide important stepping stones towards the development of chemical compounds for applications in radiopharmacy.

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BSc/MSc project: Optimization of laser ion sources with high-power pulsed Ti:sapphire lasers

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.

BSc/MSc project: Separation of niobium-93 from its isomer niobium-93m by selective laser ionization

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.

Closing the last gap for the Periodic Table’s 150th birthday

Figure: PRA 99, 062513

Timely for the “International Year of the Periodic Table of Chemical Elements” which celebrates the 150th anniversary of Mendeleev's discovery of the periodic table, a European collaboration of chemists and physicists has published the first experimental determination of the ionization potential of the lanthanide element promethium, thus closing the last remaining gap for this fundamental atomic property in the Periodic Table.

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