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Laser cooling and precision laser spectroscopy of highly charged ions are considered as frontiers of atomic physics research at heavy ion storage rings. A brief overview of the fundamentals of these powerful methods, applied to relativistic stored ion beams, is given. Preliminary results from laser cooling of lithium-like 16O5+ ion beams at a relativistic energy of 275.7 MeV/u at the heavy-ion storage ring CSRe are presented and prospects for upcoming experiments at the future facility HIAF are discussed.

An improved moveable in vacuo XUV fluorescence detection system was employed for the laser cooling of bunched relativistic (β = 0.47) carbon ions at the Experimental Storage Ring (ESR) of GSI Helmholtzzentrum Darmstadt, Germany. Strongly Doppler boosted XUV fluorescence (∼90 nm) was emitted from the ions in a forward light cone after laser excitation of the 2s–2p transition (∼155 nm) by a new tunable pulsed UV laser system (257 nm). It was shown that the detected fluorescence strongly depends on the position of the detector around the bunched ion beam and on the delay (∼ns) between the ion bunches and the laser pulses. In addition, the fluorescence information could be directly combined with the revolution frequencies of the ions (and their longitudinal momentum spread), which were recorded using the Schottky resonator at the ESR. These fluorescence detection features are required for future laser cooling experiments at highly relativistic energies (up to γ∼ 13) and high intensities (up to 1011 particles) of ion beams in the new heavy ion synchrotron SIS100 at FAIR.

Quantum electrodynamics has been tested to accuracies below the parts-per-trillion level in light-mass systems. However, tests in heavy-mass systems with a large nuclear charge have not yet reached similar accuracy. Here we report the hyperfine-structure splitting in the 1 s ground state of radioactive hydrogen-like 208 Bi 82+ . We produced the isotope in a nuclear reaction and injected the beam into a storage ring to perform laser spectroscopy on samples of 10 5 ions of Bi 82+ that have only a single remaining electron, which experiences extreme magnetic-field strengths. Our result for the hyperfine splitting is in excellent agreement with the most accurate prediction based on a combination of quantum electrodynamics calculations with an empirical treatment of the hyperfine-structure anomaly ratio extracted from laser spectroscopy on neutral atoms of 209 Bi and 208 Bi. This achievement paves the way for the most stringent test of quantum electrodynamics in strong magnetic fields and demonstrates the feasibility of laser spectroscopy on other exotic ions with low production yields. Hyperfine splitting was measured using the laser spectroscopy of accelerator-produced hydrogen-like bismuth ions. This demonstrates the feasibility of such measurements with other exotic ions with low production yields in a storage ring.