ABSTRACT
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.
ABSTRACT
We report on the successful demonstration of a novel scheme for detecting optical transitions in highly charged ions. We applied it to determine the frequency of the dipole-forbidden 2p ^{2}P_{1/2}-^{2}P_{3/2} transition in the fine structure of ^{40}Ar^{13+} using a single ion stored in the harmonic potential of a Penning trap. Our measurement scheme does not require detection of fluorescence, instead it makes use of the continuous Stern-Gerlach effect. Our value of 679.216464(4)_{stat}(5)_{syst} THz is in reasonable agreement with the current best literature values and improves its uncertainty by a factor of 24.
ABSTRACT
A portable high resolution soft x-ray and extreme ultraviolet (EUV) spectrometer has been developed for spectroscopic research at the Shanghai Electron Beam Ion Trap (EBIT) laboratory. A unique way of aligning the grazing incidence spectrometer using the zero order of the grating is introduced. This method is realized by extending the range of the movement of the CCD detector to cover the zero order. The alignment can be done in a few minutes, thus leading to a portable spectrometer. The high vacuum needed to be compatible with the EBITs is reached by mounting most of the translation and rotation stages outside the chamber. Only one high vacuum compatible linear guide is mounted inside the chamber. This is to ensure the convenient interchange of the gratings needed to enable wavelength coverage of the whole range of 10 to 500 Å. Spectra recorded with one of our low energy EBITs shows that a resolving power of above 800 can be achieved. In the slitless configuration used in this work, we found the resolving power to be limited by the width of the EBIT plasma. When mounted on the Shanghai EBIT which is a high energy EBIT and has a narrower EBIT plasma width, the estimated resolving power will be around 1400 at 221.15 Å.
