Sprecher
Beschreibung
Transition energy measurements in heavy, few-electron ions are unique tools to test bound-state quantum electrodynamics (QED) in extremely high Coulomb fields, where perturbative methods cannot be implemented. By accurately measuring the relative energies between $2p_{3/2} \to 2s_{1/2}$ transitions (of an energy of about 4.5 keV) in two-, three-, and four-electron uranium ions, we were able, for the first time in this regime, to disentangle and test separately high-order (two-loop) one-electron and two-electron QED effects and set a new important benchmark for this theory in the strong field domain [1]. The achieved accuracy of 37 parts per million allows us to discriminate between different theoretical approaches developed throughout the last decades for describing He-like systems. Such a precise measurement has been obtained by implementing a novel multi-reference method based on Doppler-tuned x-ray emission from fast ions stored in the ESR ring of the GSI/FAIR facility and using a pair of crystal diffractometers.
Experimental outlooks will also be presented, in which a new calibration scheme using a light reference ion and the implementation of a new time- and position-sensitive detector will be used. Together, these improvements are expected to reduce uncertainties to about 9 meV—ten times lower than current theoretical predictions and nuclear deformation effects. This approach opens a new pathway for probing the nuclear properties of heavy nuclei.
