Bound electron g-factor measurement by double-resonance spectroscopy on a fine-structure transitionThis paper was presented at the International Conference on Precision Physics of Simple Atomic Systems, held at École de Physique, les Houches, France, 30 May  – 4 June, 2010.

Abstract

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.

Progress in quantum electrodynamics theory of highly charged ions

“…[86]. High-precision measurements are also anticipated for B-like 40 Ar 13+ and 40 Ca 15+ [87,88]. The investigations of the g factor of few-electron ions provide an access to the many-electron QED corrections.…”

Experimental access to higher-order Zeeman effects by precision spectroscopy of highly charged ions in a Penning trap

“…The first stage has 40 W cooling power at 45 K and maintains the temperature of the radiation shield; the second stage inside the radiation shield has 1 W cooling power at 4.2 K and keeps the trap and its electronics at liquid-helium temperature. Several aspects of this setup have already been described in [16,41]. The working principle of in-trap ion production and transfer is similar to that in [42].…”

“…We are currently setting up a laser-microwave double-resonance spectroscopy experiment with highly charged ions in a Penning trap, which combines precise spectroscopy of both optical transitions and microwave Zeeman splittings [15,16]. The experiment aims at spectroscopic precision measurements of such energy level splittings and magnetic moments of bound electrons on the ppb level of accuracy and better.…”

Penning-trap experiments for spectroscopy of highly-charged ions at HITRAP

“…We are currently commissioning the system with such internally produced ions. A connection to the HITRAP low-energy beam line [22,23] is under construction and measurements with heavy, highly charged ions up to U 91+ are foreseen. From the observed charge state lifetime against electron capture from residual gas of roughly one day for ions such as Ar 13+ (see figure 5), we derive a background pressure of less than 10 −13 mbar and corresponding lifetimes of several hours for ions of even the highest charge states, which is sufficient for the intended measurements.…”