Abstract
The LIBELLE experiment performed at the experimental storage ring at the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, Germany, has successfully determined the ground state hyperfine (HFS) splittings in hydrogen-like () and lithium-like () bismuth. The study of HFS transitions in highly charged ions enables precision tests of QED in extreme electric and magnetic fields otherwise not attainable in laboratory experiments. Besides the transition wavelengths the time-resolved detection of fluorescence photons following the excitation of the ions by a pulsed laser system also allows the extraction of lifetimes of the upper HFS levels and g-factors of the bound 1s and 2s electrons for both charge states. While the lifetime of the upper HFS state in has already been measured in earlier experiments, an experimental value for lifetime of this state in is reported for the first time in this work.
Highlights
While the prime target of the experiment was the determination of the transition energies, the time-resolved acquisition of the fluorescence photons emitted during the de-excitation of the ions allowed us to extract lifetimes of the upper HFS states and, together with the measured transition energies, to calculate g-factors of the bound 1s electron for H-like bismuth and of the 2s electron for Li-like bismuth
While the time interval of 33.3 ms between individual laser pulses is sufficiently long for the excited HFS state in H-like bismuth to decay completely, the longer lifetime of the upper HFS state in Li-like Bi of about 118 ms at β = 0.71 requires a shutter system to periodically block the laser for several lifetimes, allowing the observation of a sufficiently large part of the decay curve to obtain a good fit of the lifetime in the laboratory frame τlab
The lifetimes of the upper HFS states in 209Bi82+ and, for the first time, in 209Bi80+ have been measured by the LIBELLE experiment and are compared to previous experimental and/or theoretical results
Summary
Laboratory with conventional methods (like lasers and superconducting magnets) Interesting in this context is the study of hyperfine transitions in hydrogen-like and lithium-like ions. The LIBELLE13 experiment was for the first time able to measure H-like and Li-like HFS splittings in the same isotope [4] with sufficient precision to allow for a test of bound state QED calculations. While the prime target of the experiment was the determination of the transition energies, the time-resolved acquisition of the fluorescence photons emitted during the de-excitation of the ions allowed us to extract lifetimes of the upper HFS states and, together with the measured transition energies, to calculate g-factors of the bound 1s electron for H-like bismuth and of the 2s electron for Li-like bismuth. The following sections will provide details on the experimental procedure and analysis of the data required to extract the aforementioned quantities
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