Heidelberg 2015 – scientific programme

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A: Fachverband Atomphysik

A 1: Precision spectroscopy of atoms and ions I (with Q)

A 1.3: Talk

Monday, March 23, 2015, 12:00–12:15, C/HSW

Determination of ground-state hyperfine splitting energies in highly charged bismuth ions — •Johannes Ullmann für die LIBELLE Kollaboration — Institut für Kernphysik, Technische Universität Darmstadt, Germany — Helmholtz Institut Jena, Germany

While quantum electrodynamics (QED) is usually referred to as the most accurately tested theory, its consistency for bound electrons in strong fields is still to be tested more rigourosly. The strongest static magnetic fields available in the laboratory are experienced by ground-state electrons of highly charged, heavy ions which can be probed by hyperfine transition spectroscopy.

The transition in Li-like Bismuth was directly observed for the first time in 2011 at the experimental storage ring ESR located at GSI Darmstadt, the major improvement being an optimized detection system collecting the Doppler-shifted photons. Yet the accuracy of the result was limited by the calibration of the electron cooler voltage, determining the ion velocity which is required to transform the measured transition wavelength to the rest frame of the ion. We were able to reduce the uncertainties in nearly all experimental parameters in a second beamtime at the ESR in 2014. The continuous in-situ measurement of the electron cooler voltage using a precise high voltage divider provided by the Physikalisch-Technische Bundesanstalt minimized the main uncertainty of 2011. We will present results of the transition wavelength in H-like and Li-like ions and discuss the relevance for a test of strong-field bound-state QED.