Tests Of QED Research Articles

Towards tests of QED in Lamb‐shift measurements of highly charged ions

AbstractThe present status of theoretical predictions for the Lamb shift in heavy few‐electron ions is reviewed. We compare theoretical predictions with experimental data and discuss perspectives of testing quantum electrodynamics in a new region: the region of the strongest electrical fields available at present for experimental study. Copyright © 2003 John Wiley & Sons, Ltd.

The measurement of the electronic g-factor in hydrogen-like ions --A promising tool for determining fundamental and nuclear constants

We describe a double—Penning-trap experiment suitable for testing QED in strong fields by determining the electronic g-factor of a single hydrogen-like ion in its ground state. Our measurements on 12C5+ reach a relative accuracy of 2 × 10−9, where the largest uncertainty results from the mass of the electron. Together with equally precise theoretical predictions therefore, it is possible to evaluate a new value for the electron’s mass. The possibilities to obtain other fundamental constants and nuclear parameters are lined out.

Nuclear-polarization correction to the bound-electron g factor in heavy hydrogenlike ions.

The influence of nuclear polarization on the bound-electron g factor in heavy hydrogenlike ions is investigated. Numerical calculations are performed for the K- and L-shell electrons taking into account the dominant virtual nuclear excitations. This determines the ultimate limit for tests of QED utilizing measurements of the bound-electron g factor in highly charged ions.

Study of multiphoton final states and tests of QED in e+e− collisions at up to 209 GeV

The process e+ e- -> n gamma with n>=2 is studied at centre-of-mass energies ranging from \root(s)=192 to 208 GeV. The data sample corresponds to a total integrated luminosity of 427 1/pb. The total and differential cross sections are found to be in agreement with the QED expectations. Using all the data collected with the L3 detector above the Z pole, limits on deviations from QED, excited electrons, contact interactions, extra space dimensions and excited spin-3/2 leptons are set.

Hyperfine structure of the ground and first excited states in light hydrogen-like atoms and high-precision tests of QED

We consider hyperfine splitting of 1s and, in part, of 2s levels in light hydrogen-like atoms: hydrogen, deuterium, tritium, helium-3 ion, muonium and positronium. We discuss present status of precision theory and experiment for the hfs intervals. We pay a special attention to a specific difference, D_{21} = 8 E_{hfs}(2s) - E_{hfs}(1s), which is known experimentally for hydrogen, deuterium and ^3He^+ ion. The difference is weakly affected by the effects of the nuclear structure and thus may be calculated with a high accuracy. We complete a calculation of the fourth order QED contributions to this difference and present here new results on corrections due to the nuclear effects. Our theoretical predictions appear to be in a fair agreement with available experimental data. Comparison of the experimental data with our examination of D_{21} allows to test the state-dependent sector of theory of the hfs separation of the 1s and 2s levels in the light hydrogen-like atoms up to 10^-8.

QED effects in Cu-like Pb recombination resonances near threshold.

In an electron-ion recombination study with Pb53+ dielectronic recombination resonances are found for as low as approximately 10(-3)-10(-4) eV relative energy. The resonances have been calculated by relativistic many-body perturbation theory and through comparison with experiment the Pb53+(4p(1/2)-4s(1/2)) energy splitting of approximately 118 eV is determined with an accuracy comparable to the position of the first few resonances, i.e., approximately 10(-3) eV. Such a precision provides a test of QED in a many-body environment at a level which can still not be reached in calculations.

Radiative Corrections in Highly Charged Ions and Tests of QED in Strong Electric and Magnetic Fields

To provide predictions of the Lamb shift of highly charged ions on the level of accuracy of about 10-6 has been achieved after exact results for the contributions of all two-photon self-energy diagrams have been performed. We report on the present status of our Lamb-shift calculations including all QED-corrections of first- and second-order in the finestructure constant α and all relevant nuclear effects. An excellent agreement between the most recent experimental data for Lamb shift of the 1s-ground state in hydrogenlike uranium can be stated. This can serve as a sensitive test of QED in the strongest electric fields accessible in nature. In a second part of this article we report about an all-order numerical evaluation of the one-photon selfenergy at low nuclear charge (Z = 1, ..., 5). A sensitive comparison of our numerical approach with analytical approach to the one-photon selfenergy confirms the consistency of these two different approaches (numerical and analytic) to very high precision.

Access to Two-Photon QED Contributions via 2s 2S1/2–2p 2P1/2 Transitions in Heavy Li-Like Ions

Wavelengths of the 2s 2S1/2–2p 2P1/2 fine structure transition in lithium-like ions in the medium heavy Z range have been measured using beam foil excitation and grazing incidence spectroscopy. The achieved precision of 70 ppm allows for a 0.1% QED test which establishes a new benchmark. It provides sensitivity to two-photon QED contributions. Very good agreement with the newest calculations based on hydrogenic wave functions and applying a strict QED formalism is observed. All accurate published data along the isoelectronic Li-like series for Z > 20 are summarized. Their values and their accuracies are compared to the calculations and to the relative QED contributions, respectively.

Measurements of2s2S1/2–2p2P1/2transition energies in lithiumlike heavy ions. III. Experimental results forSn47+andXe51+

Wavelengths of the fine-structure transition $2s{}^{2}{S}_{1/2}$--$2p{}^{2}{P}_{1/2}$ in lithiumlike ${\mathrm{Sn}}^{47+}$ and ${\mathrm{Xe}}^{51+}$ have been determined using beam foil excitation and grazing incidence spectroscopy. Transition wavelengths of $114.895\ifmmode\pm\else\textpm\fi{}0.008 \AA{}$ for ${\mathrm{Sn}}^{47+}$ and $103.475\ifmmode\pm\else\textpm\fi{}0.007 \AA{}$ for ${\mathrm{Xe}}^{51+}$ have been measured. While there has been no previous measurement of this transition in Sn, the Xe result marks an improvement in accuracy of more than an order of magnitude compared with previous experiments. The achieved precision of 70 ppm for the 1/2-1/2 transition allows for a 0.1% QED test which establishes a new benchmark for Li-like ions in the medium Z range. The experimental uncertainty is smaller than the size of the smallest calculated contribution to the transition energy.

Measurement of mirror birefringence at the sub-ppm level: Proposed application to a test of QED

We present detailed considerations on the achievable sensitivity in the measurement of birefringence using a high finesse optical cavity, emphasizing techniques based on frequency metrology. Alternative approaches of laser locking and cavity measurement techniques are discussed and demonstrated. High-precision measurements of the cavity mirror birefringence have led to the interesting observations of photorefractive activities on mirror surfaces.

Density shift and broadening of transition lines in antiprotonic helium

The density shift and broadening of the transition lines of antiprotonic helium have been evaluated in the impact approximation using an interatomic potential calculated ab initio with the symmetry-adapted perturbation theory. The results help to remove an uncertainty of up to 10 ppm in the laser spectroscopy data on antiprotonic helium and are of importance in experimental tests of bound state QED and CPT invariance.

Hard-photon production and tests of QED at LEP

The total and differential cross sections of the process e +e −→ nγ with n≥2 are measured using data collected by the L3 experiment at centre-of-mass energies of s =183 and 189 GeV . The results are in agreement with the Standard Model expectations. Limits are set on deviations from QED, contact interaction cut-off parameters and masses of excited electrons.

Measurements of2s2S1/2−2p2P1/2,3/2transition energies in lithiumlike heavy ions. II. Experimental results forAg44+and discussion along the isoelectronic series

Wavelengths of the fine structure transitions $2s{}^{2}{S}_{1/2}\ensuremath{-}2p{}^{2}{P}_{3/2}$ and $2s{}^{2}{S}_{1/2}\ensuremath{-}2p{}^{2}{P}_{1/2}$ in lithiumlike ${\mathrm{Ag}}^{44+}$ have been measured using beam-foil excitation and grazing incidence spectroscopy. The respective transition wavelengths of 40.829\ifmmode\pm\else\textpm\fi{}0.004 \AA{} and of 124.685\ifmmode\pm\else\textpm\fi{}0.009 \AA{} were not measured before for this ion. The achieved precision of 70 ppm for the 1/2-1/2 transition allows for a 0.2% QED test which sets a new benchmark in the medium Z range. Our experimental uncertainty is smaller than calculated two-photon exchange contributions to the transition energy. A summary of all published experimental data along the isoelectronic sequence for $Zg~$24, including our recent results for ${\mathrm{Ni}}^{25+}$ and ${\mathrm{Zn}}^{27+},$ is presented and compared with the best available calculations.

Laser spectroscopy of the Lamb shift in muonic hydrogen

The muonic hydrogen atom in the 2s state provides the possibility of achieving high precision laser spectroscopy experiments from which a high precision value of the proton radius can be deduced. This will ultimately allow an increased precision in the test of QED in bound systems. Important progress has been made in recent years in the ability to stop muons in a low pressure gas target and in the understanding of the 2s-metastability in muonic hydrogen. As a consequence the 2s–2p laser spectroscopy experiment is now feasible and we present here the basic experimental concept considered by our collaboration.

Recombination of HCI with Electrons – Fundamental Atomic Physics and Applications

Recent experimental studies of electron-ion recombination performed at heavy-ion storage rings as well as related theoretical work is reviewed. The topics covered are high resolution spectroscopy of doubly excited states by dielectronic recombination, relativistic effects, interference between radiative and dielectronic recombination, test of QED in high-Z HCI, recombination rate enhancement at low energies, recombination in the presence of external fields and applications to astrophysical and laboratory plasmas.

Precision Spectroscopy in He as a Test of QED

High-resolution laser-based measurements of energy levels have spurred the development and refinement of quantum electrodynamic calculations. We have extended very-high-resolution laser spectroscopy techniques into the vacuum ultraviolet wavelength region at λ ≈ 120 nm to determine the Lamb shift in the ground state of He I. The importance of this measurement to high accuracy quantum electrodynamics calculations is discussed. Details of the present measurement and future improvements are presented.

Precision X-ray Spectroscopy at the NIST Electron-Beam Ion Trap: Resolution of Major Systematic Error

Some of the most critical tests of the QED Lamb shifts are currently being pursued in the x-ray regime by investigating the core levels of medium Z atoms such as vanadium. The current approach to the measurement of the Lamb shift in such a system is outlined. We present major progress in understanding and reducing the systematic errors within our system. The error budget has been reduced to a level where critical tests of QED can be performed. Recent observations of Lyman α in hydrogenic vanadium at the NIST Electron-Beam Ion Trap are presented.

QED Effects in Strong Nuclear Fields

The present status of QED tests for heavy, highly charged ions with one or a few electrons is reviewed. The results of numerical calculations (to all orders in Za) of the Lamb shift for hydrogen-, helium- and lithium-like ions are compared with recent experimental results. Also numerical calculations of the hyperfine structure and Zeeman effect in heavy hydrogen-like ions are discussed.

High precision tests of QED and physics beyondthe standard model

High precision tests of QED and physics beyondthe standard model

Measurement of QED and Hyperfine Splitting in the2s1/2-2p3/2X-Ray Transition in Li-likeB209i80+

A measurement of the ${2s}_{1/2}\ensuremath{-}{2p}_{3/2}$ x-ray transition in trapped Li-like ${\mathrm{Bi}}^{80+}$ ions was made that resolved the $0.820\ifmmode\pm\else\textpm\fi{}0.026\mathrm{eV}$ hyperfine splitting of the $({1s}^{2}2s{)}_{F\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}4,5}$ ground configuration, providing the first such measurement in a multielectron highly charged ion. The intensity ratio of the two components is shown to be a new electron density diagnostic. The statistically averaged $2788.139\ifmmode\pm\else\textpm\fi{}0.039\mathrm{eV}$ energy of the ${2s}_{1/2}\ensuremath{-}{2p}_{3/2}$ transition provides the most accurate test of QED in a high- $Z$ ion to date, demonstrating the need for including higher-order terms in the Lamb shift calculations.