We have measured the ground-state g-factor of boronlike argon 40 Ar 13+ with a fractional uncertainty of 1.4 × 10 −9 with a single ion in the newly developed Alphatrap double Penning-trap setup. The here obtained value of g = 0.663 648 455 32(93) is in agreement with our theoretical prediction of 0.663 648 12(58). The latter is obtained accounting for quantum electrodynamics, electron correlation, and nuclear effects within the state-of-the-art theoretical methods. Our experimental result distinguishes between existing predictions that are in disagreement, and lays the foundations for an independent determination of the fine-structure constant.
The Alphatrap experiment at the Max-Planck Institute for Nuclear Physics in Heidelberg aims at probing the validity of quantum electrodynamics in extremely strong electromagnetic fields. To this end, Alphatrap will determine the value of the magnetic moment, or the g-factor, of the electron bound in highly charged ions. Quantum electrodynamics predicts this value with extraordinary precision. As the bound electron in highly charged ions is exposed to the strongest fields available for high-precision spectroscopy in the laboratory, reaching up to 10 16 V/cm in hydrogenlike lead 208 Pb 81+ , a comparison of the theoretical prediction with a measured value can yield the most stringent test of the Standard Model in strong fields. The targeted precision of eleven digits or more can be achieved by storing single highly charged ions in a cryogenic Penning trap, where its eigenfrequencies can be determined with ultra-sensitive electronics to highest precision. Additionally, the spin state can be non-destructively determined using the continuous Stern-Gerlach effect, allowing spectroscopy of the Larmor precession. Alphatrap is constructed to enable the injection and the storage of externally produced ions. The coupling to the Heidelberg EBIT gives access to even the heaviest highly charged ions and thus extends the available field strength by more than two orders of magnitude compared to previous experiments. This article describes the technical architecture and the performance of Alphatrap and summarises the experimental measurement possibilities.This article comprises parts of the thesis work of I. 1426The European Physical Journal Special Topics and served as a blueprint for the development of the other theories. Accordingly, the experimental verification of this theory is of major importance and interest. Indeed, QED is today considered to be the best tested theory of the SM. The magnetic moment associated with the spin of the electron can be calculated within the framework of QED and has thus served for experimental tests of the theory. Probably the most intriguing of these experiments is the g − 2 experiment of the free electron [1], which has determined the gyromagnetic ratio, or g-factor, of the electron up to the 13th decimal. This unique agreement of the experiment with the prediction by the SM is a far-reaching confirmation of the validity of the theory. However, in this experiment, except for the weak magnetic trapping field, the electron couples only to the vacuum field, so that non-linear effects in the field strength might go unnoticed.In order to specifically address such interactions, for example a hypothetical photon self-interaction or any other strong-field deviation of the known interactions, tests at the strongest possible electromagnetic field are desirable. Externally applied static fields are limited in strength to about 50 T for static or 300 T for pulsed magnetic fields, or to about 1600 kV/cm in vacuum gaps [2] in case of electrostatic fields. These limitations can be overcome in intense laser ...
Quantum electrodynamics (QED) is one of the most fundamental theories of physics and has been shown to be in excellent agreement with experimental results1–5. In particular, measurements of the electron’s magnetic moment (or g factor) of highly charged ions in Penning traps provide a stringent probe for QED, which allows testing of the standard model in the strongest electromagnetic fields6. When studying the differences between isotopes, many common QED contributions cancel owing to the identical electron configuration, making it possible to resolve the intricate effects stemming from the nuclear differences. Experimentally, however, this quickly becomes limited, particularly by the precision of the ion masses or the magnetic field stability7. Here we report on a measurement technique that overcomes these limitations by co-trapping two highly charged ions and measuring the difference in their g factors directly. We apply a dual Ramsey-type measurement scheme with the ions locked on a common magnetron orbit8, separated by only a few hundred micrometres, to coherently extract the spin precession frequency difference. We have measured the isotopic shift of the bound-electron g factor of the isotopes 20Ne9+ and 22Ne9+ to 0.56-parts-per-trillion (5.6 × 10−13) precision relative to their g factors, an improvement of about two orders of magnitude compared with state-of-the-art techniques7. This resolves the QED contribution to the nuclear recoil, accurately validates the corresponding theory and offers an alternative approach to set constraints on new physics.
The coupling of the motion of two ion species in separate Penning traps via a common tank circuit is discussed. The enhancement of the coupling assisted by the tank circuit is demonstrated by an avoided crossing behavior measurement of the motional modes of two coupled ions. An intermittent laser cooling method for sympathetic cooling is proposed and a theoretical description is provided. The technique enables tuning of the coupling strength between two ion species in separate traps and thus allows for efficient sympathetic cooling of an arbitrary type of single ion for high-precision Penning-trap experiments. IntroductionPenning traps have been proven as a versatile tool for fundamental physics [1,2] as well as in quantum science. [3,4] A multitude of high-precision measurements have been performed at Penningtrap facilities, such as measurements of atomic masses, [5][6][7][8][9][10][11] magnetic moments of elementary particles, for instance the free [12] and bound electron, [13,14] proton [15] and antiproton, [16] and laser spectroscopy of a single highly charged ion (HCI). [17] These experiments are dedicated to testing pillars of the Standard Model
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