Giersch Excellence Grant 2015 for Johannes Ullmann
Johannes Ullmann received the Giersch Excellence Grant for his works on the determination of the hyperfine splitting energy of the ground state of hydrogen and lithium like Bismuth by laser spectroscopy. The Experiment was conducted at the experimental storage ring of the GSI Helmholtz Center for Heavy Ion Research in Darmstadt and allows a precise test of quantum electrodynamics in extreme electric and magnetic fields.
Uncertainties in the theoretical prediction of nuclear effects on the hyperfine splitting were eliminated by measuring two charge states of the same isotope. Although the hyperfine splitting energy in hydrogen like Bismuth is known since 1994, the resonance in the lithium like charge state was not found until 2011. Due to too large uncertainties in the determination of the ions' velocity, no accurate value could be determined then. „Thanks to an in-situ high voltage measurement at the GSI storage ring in combination with extensive improvements of detection systems and data acquisition, the uncertainty could be reduced by one order of magnitude“, Ullmann explains, who does his PhD at the University Jena and GSI. In collaboration with high voltage experts of Physikalisch-Technische Bundesanstalt, the national metrology institute of Germany and detector specialists of University Münster and the group of Professor Nörtershäuser at TU Darmstadt he conducted the experiment.
Every year up to 24 PhD candidates of the graduate school HGS-HIRe get the Giersch Excellence Grant, which is endowed with 2500 Euro. At the ceremony which took place at Campus Riedberg the awardees of the Giersch PostDoc Startup 2015 also were announced. All in all the Giersch Foundation awarded young researchers with 100 000 Euro.