In the Alphatrap experiment, the g factor of boronlike ^{118}Sn^{45+} has been measured with a 0.5 ppb uncertainty. This is the first high-precision measurement of the g factor of a heavy boronlike ion. The measured value of 0.6 447 038 265(4) is consistent with the presented ab initio state-of-the-art theory calculations, which predict a value of 0.64 470 29(8). So far, the only boronlike ion of which the g factor was measured with high precision has been ^{40}Ar^{13+}. The measurement presented here therefore tests quantum electrodynamics as well as many-electron interactions at much higher Z. Furthermore, we discuss the potential for an independent determination of the fine-structure constant α, which can be achieved with a specific difference of g factors, combining the presented results with the recent electron g-factor measurement of hydrogenlike tin.

We present the measurements of individual bound electron g factors of ^{20}Ne^{9+} and ^{22}Ne^{9+} on the relative level of 0.1 parts per billion. The comparison with theory represents the most stringent test of bound-state QED in strong electric fields. A dedicated mass measurement results in m(^{20}Ne)=19.992 440 168 77(9)  u, which improves the current literature value by a factor of 18, disagrees by 4 standard deviations, and represents the most precisely measured mass value in atomic mass units. Together, these measurements yield an electron mass on the relative level of 0.1 ppb with m_{e}=5.485 799 090 99(59)×10^{-4}  u as well as a factor of seven improved m(^{22}Ne)=21.991 385 098 2(26)  u.

Inner-shell electrons naturally sense the electric field close to the nucleus, which can reach extreme values beyond 10 15 V cm −1 for the innermost electrons 1 . Especially in few-electron, highly charged ions, the interaction with the electromagnetic fields can be accurately calculated within quantum electrodynamics (QED), rendering these ions good candidates to test the validity of QED in strong fields. Consequently, their Lamb shifts were intensively studied in the past several decades 2 , 3 . Another approach is the measurement of gyromagnetic factors ( g factors) in highly charged ions 4 – 7 . However, so far, either experimental accuracy or small field strength in low- Z ions 5 , 6 limited the stringency of these QED tests. Here we report on our high-precision, high-field test of QED in hydrogen-like 118 Sn 49+ . The highly charged ions were produced with the Heidelberg electron beam ion trap (EBIT) 8 and injected into the ALPHATRAP Penning-trap setup 9 , in which the bound-electron g factor was measured with a precision of 0.5 parts per billion (ppb). For comparison, we present state-of-the-art theory calculations, which together test the underlying QED to about 0.012%, yielding a stringent test in the strong-field regime. With this measurement, we challenge the best tests by means of the Lamb shift and, with anticipated advances in the g -factor theory, surpass them by more than an order of magnitude.

We present the measurements of individual bound electron g factors of Ne-20(9+) and Ne-22(9+) on the relative level of 0.1 parts per billion. The comparison with theory represents the most stringent test of bound-state QED in strong electric fields. A dedicated mass measurement results in m(Ne-20) = 19.992 440 168 77(9) u, which improves the current literature value by a factor of 18, disagrees by 4 standard deviations, and represents the most precisely measured mass value in atomic mass units. Together, these measurements yield an electron mass on the relative level of 0.1 ppb with m(e) = 5.485 799 090 99(59) x 10(-4) u as well as a factor of seven improved m(22) = 21.991 385 098 2(26) u.

We present the measurements of individual bound electron $g$ factors of $^{20}\text{Ne}^{9+}$ and $^{22}\text{Ne}^{9+}$ on the relative level of $0.1\,\text{parts}$ per billion. The comparison with theory represents the most stringent test of bound-state QED in strong electric fields. A dedicated mass measurement results in $m\left(^{20}\text{Ne}\right)=19.992\,440\,168\,77\,(9)\,\text{u}$, which improves the current literature value by a factor of nineteen, disagrees by $4$ standard deviations and represents the most precisely measured mass value in atomic mass units. Together, these measurements yield an electron mass on the relative level of $0.1\,\text{ppb}$ with $m_{\text{e}}=5.485\,799\,090\,99\,(59) \times 10^{-4}\,\text{u}$ as well as a factor of eight improved $m\left(^{22}\text{Ne}\right)=21.991\,385\,098\,2\,(26)\,\text{u}$.

We present the measurements of individual bound electron $g$ factors of ${^{20}\mathrm{Ne}}^{9+}$ and ${^{22}\mathrm{Ne}}^{9+}$ on the relative level of 0.1 parts per billion. The comparison with theory represents the most stringent test of bound-state QED in strong electric fields. A dedicated mass measurement results in $m(^{20}\mathrm{Ne})=\phantom{\rule{0ex}{0ex}}19.992\text{ }440\text{ }168\text{ }77(9)\text{ }\text{ }\mathrm{u}$, which improves the current literature value by a factor of 18, disagrees by 4 standard deviations, and represents the most precisely measured mass value in atomic mass units. Together, these measurements yield an electron mass on the relative level of 0.1 ppb with ${m}_{\mathrm{e}}=5.485\text{ }799\text{ }090\text{ }99(59)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\text{ }\text{ }\mathrm{u}$ as well as a factor of seven improved $m(^{22}\mathrm{Ne})=21.991\text{ }385\text{ }098\text{ }2(26)\text{ }\text{ }\mathrm{u}$.

We present the measurements of individual bound electron g factors of ^20Ne^9+ and ^22Ne^9+ on the relative level of 0.1 parts per billion. The comparison with theory represents the most stringent test of bound-state QED in strong electric fields. A dedicated mass measurement results in m(^20Ne)=19.992 440 168 77 (9) u, which improves the current literature value by a factor of nineteen, disagrees by 4 standard deviations and represents the most precisely measured mass value in atomic mass units. Together, these measurements yield an electron mass on the relative level of 0.1 ppb with m_e=5.485 799 090 99 (59) × 10^-4 u as well as a factor of eight improved m(^22Ne)=21.991 385 098 2 (26) u.

An ion in a Penning trap induces image charges on the surfaces of the trap electrodes. These induced image charges are used to detect the ion's motional frequencies, but they also create an additional electric field, which shifts the free-space cyclotron frequency typically at a relative level of several 10(-11). In various high-precision Penning-trap experiments, systematics and their uncertainties are dominated by this so-called image charge shift (ICS). The ICS is investigated in this work by a finite-element simulation and by a dedicated measurement technique. Theoretical and experimental results are in excellent agreement. The measurement is using singly stored ions alternately measured in the same Penning trap. For the determination of the ion's magnetron frequency with relative precision of better than 10 parts per billion, a Ramsey-like technique has been developed. In addition, numerical calculations are carried out for other Penning traps and agree with older ICS measurements.

The precise knowledge of the atomic masses of light atomic nuclei, e.g. the proton, deuteron, triton and helion, is of great importance for several fundamental tests in physics. However, the latest high-precision measurements of these masses carried out at different mass spectrometers indicate an inconsistency of five standard deviations. To determine the masses of the lightest ions with a relative precision of a few parts per trillion and investigate this mass problem a cryogenic multi-Penning trap setup, LIONTRAP (Light ION TRAP), was constructed. This allows an independent and more precise determination of the relevant atomic masses by measuring the cyclotron frequency of single trapped ions in comparison to that of a single carbon ion. In this paper the measurement concept and the first doubly compensated cylindrical electrode Penning trap, are presented. Moreover, the analysis of the first measurement campaigns of the proton's and oxygen's atomic mass is described in detail, resulting in mp = 1.007 276 466 598 (33) u and m(16O)= 15.994 914 619 37 (87) u. The results on these data sets have already been presented in [F. Heisse et al., Phys. Rev. Lett. 119, 033001 (2017)]. For the proton's atomic mass, the uncertainty was improved by a factor of three compared to the 2014 CODATA value.

The recently established agreement between experiment and theory for the g factors of lithiumlike silicon and calcium ions manifests the most stringent test of the many-electron bound-state quantum electrodynamics (QED) effects in the presence of a magnetic field. In this Letter, we present a significant simultaneous improvement of both theoretical g_{th}=2.000 889 894 4 (34) and experimental g_{exp}=2.000 889 888 45 (14) values of the g factor of lithiumlike silicon ^{28}Si^{11+}. The theoretical precision now is limited by the many-electron two-loop contributions of the bound-state QED. The experimental value is accurate enough to test these contributions on a few percent level.