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A weighted difference of the g factors of the H- and Li-like ions of the same element is theoretically studied and optimized in order to maximize the cancellation of nuclear effects between the two charge states. We show that this weighted difference and its combination for two different elements can be used to extract a value for the fine-structure constant from near-future bound-electron g factor experiments with an accuracy competitive with or better than the present literature value. [ABSTRACT FROM AUTHOR]

We measure the absolute frequency of seven out of the nine allowed transitions between the 23S and 23P hyperfine manifolds in a metastable 3He beam by using an optical frequency comb synthesizer-assisted spectrometer. The relative uncertainty of our measurements ranges from 1 × 10-11 to 5 × 10-12, which is, to our knowledge, the most precise result for any optical 3He transition to date. The resulting 23P-23S centroid frequency is 276702 827 204.8(2.4) kHz. Comparing this value with the known result for the 4He centroid and performing ab initio QED calculations of the 4He-3He isotope shift, we extract the difference of the squared nuclear charge radii δr2 of 3He and 4He. Our result for δr2 = 1.074(3) fm2 disagrees by about 4&b.sigma; with the recent determination [R. van Rooij et al. Science 333, 196 (2011)]. [ABSTRACT FROM AUTHOR]

We have measured the ground-state g factor of boronlike argon 40Ar13+ with a fractional uncertainty of 1.4×10-9 with a single ion in the newly developed Alphatrap double Penning-trap setup. The value of g=0.663 648 455 32(93) obtained here 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. [ABSTRACT FROM AUTHOR]

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., (© 2023. The Author(s).)

We report calculations of Delbrück scattering that include all-order Coulomb corrections for photon energies above the threshold of electron-positron pair creation. Our approach is based on the application of the Dirac-Coulomb Green's function and accounts for the interaction between the virtual electron-positron pair and the nucleus to all orders in the nuclear binding strength parameter αZ. Practical calculations are performed for the scattering of 2.754 MeV photons off plutonium atoms. We find that including the Coulomb corrections enhances the scattering cross section by up to 50% in this case. The obtained results resolve the long-standing discrepancy between experimental data and theoretical predictions and demonstrate that an accurate treatment of the Coulomb corrections is crucial for the interpretation of existing and guidance of future Delbrück scattering experiments on heavy atoms.

We demonstrate a widely applicable technique to absolutely calibrate the energy scale of x-ray spectra with experimentally well-known and accurately calculable transitions of highly charged ions, allowing us to measure the K-shell Rydberg spectrum of molecular O_{2} with 8 meV uncertainty. We reveal a systematic ∼450  meV shift from previous literature values, and settle an extraordinary discrepancy between astrophysical and laboratory measurements of neutral atomic oxygen, the latter being calibrated against the aforementioned O_{2} literature values. Because of the widespread use of such, now deprecated, references, our method impacts on many branches of x-ray absorption spectroscopy. Moreover, it potentially reduces absolute uncertainties there to below the meV level.

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 value of g=0.663 648 455 32(93) obtained here 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 complete gauge-invariant set of the one-loop QED corrections to the parity-nonconserving 6s-7s amplitude in 133Cs is evaluated to all orders in alphaZ using a local version of the Dirac-Hartree-Fock potential. The calculations are performed in both length and velocity gauges for the absorbed photon. The total binding QED correction is found to be -0.27(3)%. The weak charge of 133Cs, derived using two most accurate values of the vector transition polarizability beta, is Q(W)=-72.57(46) for beta=26.957(51)a(3)(B) and Q(W)=-73.09(54) for beta=27.15(11)a(3)(B). The first value deviates by 1.1sigma from the prediction of the standard model, while the second one is in perfect agreement with it.

A complete evaluation of the two-loop self-energy diagrams to all orders in Zalpha is presented for the ground state of H-like ions with Z > or =40.

The one-loop self-energy correction to the 1s-electron g factor is evaluated to all orders in Zalpha with an accuracy essentially better than that of previous calculations of this correction. As a result, the uncertainty of the theoretical prediction for the bound-electron g factor in H-like carbon is reduced by a factor of 3. This improves the total accuracy of the recent electron-mass determination [T. Beier, Phys. Rev. Lett. 88, 011603 (2002)]]. The new value of the electron mass is found to be m(e)=0.000 548 579 909 3 (3) u.

The nuclear-recoil correction to the bound-electron g factor in H-like atoms is calculated to first order in m/M and to all orders in alphaZ. The calculation is performed in the range Z = 1--100. A large contribution of terms of order (alphaZ)(5) and higher is found. Even for hydrogen, the higher-order correction exceeds the (alphaZ)(4) term, while for uranium it is above the leading (alphaZ)(2) correction. As a result, one of the main sources of the theoretical uncertainty for the bound-electron g factor is eliminated.

The contribution of order alpha(2)(Zalpha)(6)ln (3)(Zalpha)(-2) to the ground-state Lamb shift in hydrogen induced by the loop-after-loop diagram is evaluated analytically. An additional contribution of this order is found compared to the previous calculation by Karshenboim [Sov. Phys. JETP 76, 541 (1993)]. As a result, agreement is achieved for this correction between different numerical and analytical methods.