"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."
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 https://www.appliedphotonics.de/poster-awards/.
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.
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.
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.
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.
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.
Vom 28. Mai bis zum 2. Juni findet in Keystone, Colorado die dritte „International Conference on Advances in Radioactive Isotope Science - ARIS 2017“ statt. Auf der Flagship-Konferenz des Gebiets der Untersuchung seltener Isotope stellen Vertreter der weltweit führenden Forschungseinrichtungen aktuelle Entwicklungen und Ergebnisse vor. Die Arbeitsgruppe LARISSA ist durch Reinhard Heinke vertreten und präsentiert die Aufrüstung der Ionenquelle LIST zur Anwendung für hochauflösende Spektroskopie und isomerenselektive Laserresonanzionisation an on-line-Isotopenseparatoren wie CERN-ISOLDE: „Towards On-line High-resolution In-source Laser Spectroscopy: A Perpendicular Laser – Atom Beam Upgrade for the LIST“. Die Posterpräsentation findet am Dienstag, den 30. Mai von 19 bis 21 Uhr statt.
Die vorangegangenen Arbeiten wurden in Kooperation mit dem Laserionenquellenteam von ISOLDE und Vertretern der Super-Heavy-Elements-Gruppe der GSI durchgeführt. Die Veröffentlichung der Ergebnisse ist in Vorbereitung.
Das in der AG LARISSA entwickelte Design der hochrepetierenden Titan:Saphir-Laser erhielt kürzlich ein umfassendes Update. Die neuste Generation dieser Laser wird inzwischen im Rahmen unserer internationalen Kollaborationen an verschiedenen On-line Einrichtungen eingesetzt. Ein Set an Lasern wird beim Low-Energy-Branch des MARA-Experiments an der Universität Jyväskylä (Finnland) Einsatz finden und helfen protonenreiche Radionuklide zu untersuchen.