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Outstanding doctoral theses receive awards at DESY
Alexander Knetsch and Stefan Zeller have been awarded the 2018 doctoral students’ prize by the Association of the Friends and Supporters of DESY (VFFD). The prize was presented to them yesterday evening as part of DESY’s Science Day in recognition of their excellent doctoral theses.

From left: DESY Director Helmut Dosch, awardees Alexander Knetsch and Stefan Zeller, Friedrich-Wilhelm Büßer, Chairperson of the VFFD (photo: DESY/B. Stachowske).
Stefan Zeller, from Frankfurt, started studying physics in 2005 at the Goethe University in Frankfurt. In 2012, he was awarded his master’s degree for a paper in the field of nuclear, molecular and ion physics. He received a doctoral scholarship from the Helmholtz International Centre FAIR (Facility for Antiproton and Ion Research) and took part in the programme of the Helmholtz Graduate School for Hadron and Ion Research. In 2016, he was awarded the Helmholtz Prize for Precision Measurement in Fundamental Research for measuring the binding energies of molecular quantum halos with nanoelectronvolt precision. In his doctoral thesis entitled “The Helium Dimer”, which Zeller wrote at the Goethe University in Frankfurt, he used the free-electron laser FLASH to measure the distribution of atoms along the weakest naturally existing bond between two helium atoms. Although it was known that two helium atoms form an extremely large molecule, no one had yet actually managed to observe the structure of these ultra-cold helium molecules. The group of scientists working with Stefan Zeller used the extreme brightness of FLASH to remove electrons from the helium molecule in a carefully controlled way, while measuring its shape with extreme precision. The same technology can be applied to many other molecules having an even more mysterious structure.