Precise determination of bound-electron g-factors in highly charged ions provides stringent tests for state of the art theoretical calculations. The scope reaches from relativistic electron-correlation effects on the one hand to bound-state QED terms on the other. Besides, the investigation can contribute to the determination of the fine-structure constant α. In a first approach with boron-like ions of spinless nuclei (e.g., 40Ar13+ and 40Ca15+), we will excite the 22P1/2 – 22P3/2 fine-structure transition with laser radiation and probe microwave transitions between Zeeman sublevels. From this laser-microwave double-resonance technique the g-factor can be determined on a ppb level of accuracy. We have prepared a cryogenic trap assembly with a creation trap and a spectroscopy trap — a half-open compensated cylindrical Penning trap. Argon gas will be injected through a remotely controlled valve, working at cryogenic temperature and in the field of a superconducting magnet. Ions are produced by electron impact ionization and transferred to the spectroscopy trap. In the future, the trap will be connected to the HITRAP facility at GSI, and the method will be applied to hyperfine-structure transitions of hydrogen-like heavy ions to measure electronic and nuclear magnetic moments. We present important techniques employed in the experiment.
The Chao matrix formalism allows analytic calculations of a beam's polarization behavior inside a spin resonance. We recently tested its prediction of polarization oscillations occurring in a stored beam of polarized particles near a spin resonance. Using a 1:85 GeV=c polarized deuteron beam stored in the COoler SYnchrotron, we swept a new rf solenoid's frequency rather rapidly through 400 Hz during 100 ms, while varying the distance between the sweep's end frequency and the central frequency of an rf-induced spin resonance. Our measurements of the deuteron's polarization near and inside the resonance agree with the Chao formalism's predicted oscillations.
Precise determination of bound-electron g-factors in heavy highly-charged ions (e.g. Bi 82+ , U 91+ ) provides a stringent test of bound-state QED in extreme fields. With a laser-microwave double-resonance technique we will probe the microwave transitions between the Zeeman sub-levels of the hyperfine structure in highly charged ions. From this the bound electron g-factor g J can be determined. We present the experimental progress of this novel method to measure the g-factor of the bound electron in highly charged ions.
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