864 hours of measurement time
Regensburg researchers succeed with long-term project proposal at the European Synchrotron
28. June 2024
Sometimes it doesn't take many words to announce a big decision. This was the case for Dr Michael Bodensteiner from the Faculty of Chemistry and Pharmacy at the University of Regensburg at the beginning of June. "The long-term project status is awarded for 3 years from 2024/II to 2027/I," it said in a brief email. The researcher's delight at these simple lines could not have been greater. For him and his team, the approval means secure and regular access to the European Synchrotron Radiation Facility (ESRF), a large multinational research centre and the largest electron synchrotron in Europe based in Grenoble. Bodensteiner received the grant for his project "Making crystallography better the anomalous way - towards routine application of experimental anomalous dispersion corrections".
"It's a great privilege to be given so much beam time at this unique particle accelerator," remarks the chemist. Normally, you would apply for beam time for your experiments in half-yearly review cycles, and these are then allocated in eight-hour shifts. In the international competition with applications from all kinds of research fields that require one of the most powerful X-ray sources in the world, it is not uncommon to be left empty-handed. It is therefore even more satisfying for the scientist and his fellow researchers that they do not have to worry about proposal writing for the next three years: they now have a total of 36 days, worth roughly €720,000, at their disposal for their project.
Michael Bodensteiner works in the X-ray structural analysis department of the Central Analytical Service on determining the structure of single crystals. The X-ray beam is diffracted by the regular lattice structure of a crystal and produces a pattern of light spots of different brightness on a detector. The experiment can be simulated on a computer and a theoretical diffraction pattern can be generated from a chemical structure of the underlying compound making up the crystal, which is then optimised until it matches the measured data as closely as possible. However, this matching requires a whole series of corrections to both the measured data and the model, which are usually only rather generic and made based on generalised parameters. Of particular importance, for example, is the X-ray absorption correction, which leads to a reduction in the measured X-ray intensity depending on the atomic composition of the compound under investigation. This effect is utilised particularly in the method of X-ray absorption spectroscopy, which is used for elucidation of the crystal structural, but more commonly also for determining the physical and chemical properties of a material. A further parametric correction is applied to the structural model for so-called anomalous scattering. This effect is related to absorption and has an analogue in the concept of the optical refractive index.
The Helmholtz-Zentrum Dresden-Rossendorf (HZDR) operates a research station at the ESRF, the so-called Rossendorf Beamline (ROBL), which specialises precisely in these two methods of X-ray absorption and diffraction and is therefore perfectly suited for the experiments within the scope of the project. In addition, the HZDR's research focus is on radiochemistry, i.e. the investigation of substances containing heavy radioactive elements. Such compounds are precisely where the effects of absorption and anomalous scattering are strongest. The researcher teams are also planning further joint developments to the beamline, that will then also be available to other scientists, which is one of the reasons why the HZDR is supporting the project with beam time from its own allotment. Pooling efforts was the only way to obtain approval for such an extensive measurement campaign.
The Regensburg scientists and Dr Christoph Hennig from the HZDR have been collaborating closely for more than three years, resulting in several publications as well as a Lieselotte Templeton Prize from the German Society of Crystallography for the master’s thesis of Bodensteiner’s student Florian Meurer. The awardee is now a doctoral student on a scholarship from the Studienstiftung des deutschen Volkes and is investigating the various aspects of anomalous dispersion and absorption of X-rays. Most recently, he was given the opportunity to work with radioactive substances at the Rossendorf Beamline for five months as part of the project "AcE: Fundamental investigations into the immobilisation of actinides by incorporation into solid phases relevant for final disposal", funded by the German Federal Ministry of Education and Research, and to expand his knowledge in this area.
Michael Bodensteiner himself is currently working on his habilitation in inorganic chemistry, which focuses on the "special effects" of anomalous dispersion. His aim is to be able to draw conclusions about the chemical properties and, indirectly, the reactivity of the substances analysed from the experimentally determined parameters. The approval from Grenoble came just in time for the interim evaluation of his habilitation - the timing could not have been better.
Dr. Michael Bodensteiner in his lab © Karlheinz Huber/daskleinefotoatelier.de
Information/Contact
Dr. Michael Bodensteiner
Universität Regensburg
Fakultät für Chemie und Pharmazie
Betriebseinheit Zentrale Analytik – Röntgenstrukturanalyse
Tel.: +49 (0) 941 943-4445
E-Mail: michael.bodensteiner@ur.de
