摘要:

A QED treatment of the spectra of highly-charged ions analogous to the QED treatment of the electrongfactor is advocated. In both cases a well-defined, rapidly converging set of Feynman diagrams exists that need be considered only to relatively low order in order to provide highly accurate theoretical predictions. We demonstrate this for lithiumlike bismuth, considering diagrams involving one, two, and three photons. One set of two-photon diagrams involves the two-loop Lamb shift, and we show how the size of this effect can be inferred from a recent experimental measurement. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57482

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The measurement of the anomalous magnetic moment of the electron provides the highest precision test of QED, or the most precise measurement of the fine structure constant. In order to improve this measurement beyond the 1ppb level a number of systematics have to be investigated and reduced. We report on the current status of this effort. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57452

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Theory of quantum electrodynamic and of nuclear effects in highly charged ions is reviewed. The currently available theoretical results for the Lamb shift, the hyperfine structure splitting, and the bound-electron g-factor in high-Z few-electron atoms are compared with recent experiments. A special attention is focused on testing quantum electrodynamics in domains which were not available before. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57463

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

We are aiming at predictions for the Lamb shift in hydrogen-like systems with a relative accuracy of10−6.This necessitates calculations of all radiative corrections of first and second order in &agr; but exact in the coupling constantZ&agr;to the external Coulomb field. Results for all known corrections including unclear structure effects are presented for the 1S-ground state in lead82208Pb81+and uranium92238U91+.©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57473

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

For bound systems with a small atomic numberZ, numerical evaluations of self-energy corrections, which are non-perturbative in the binding field, entail severe numerical cancellations at intermediate stages of the calculation. This paper reports on a result for the non-perturbative self-energy remainder functionGSEin atomic hydrogen with a relative accuracy of10−5.We discuss consistency checks on the results of numerical Lamb shift calculations in systems with a small atomic number. The precise determination of radiative corrections in low-Zbound systems is of crucial importance for the interpretation of precision measurements in atoms, for tests of quantum electrodynamics and for the determination of fundamental constants. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57437

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

We report on the first direct measurement of the g-factor of a highly charged ion. The experimental determination of the magnetic moment (g-factor) of the bound electron in hydrogen-like ions is an important test of the theory of Quantum Electrodynamics in strong nuclear Coulomb fields. For this purpose a single hydrogen-like ion is stored in the magnetic field of a Penning trap. The g-factor is measured by inducing spin flip transitions with a microwave field at the Larmor precession frequency of the bound electron. The magnetic field is calibrated by measuring the cyclotron frequency of the stored ion. The first results were obtained for a hydrogen-like carbon ion(C5+).The experimental precision is high enough to verify the relativistic contribution to the g-factor on the10−3level. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57483

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

A new and improved experiment for measuring the muon magnetic anomaly at the Brookhaven National Laboratory (BNL) was successfully started and has yielded first results. New major components of the experiment include a superferric storage ring, a superconducting inflector, electrostatic quadrupoles, lead-scintillating fiber electron calorimeters and a high precision NMR magnetic field measurement and control system. The first measurement of the ratio R of the spin precession frequency of the positive muon relative to that of a free proton givesR=(3.707&hthinsp;219±0.000&hthinsp;048)×10−3.It is similar in accuracy and in good agreement with previous CERN measurements for&mgr;+and&mgr;−.A muon kicker has been installed to boost the number of stored particles in the storage ring magnet and was successfully commissioned recently. The data acquired so far is expected to lower significantly the uncertainty inR. First extensive data-taking will start soon. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57438

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

We have performed Laser-microwave double and triple resonance experiments on clouds ofBa+ions confined in a Penning ion trap to induce and detect electronic and nuclear spin flip transitions. We used collisions with buffer gas molecules in the trap to cool the ions to the ambient temperature and to quench a long lived metastable state, in which population trapping might occur. Loss of ions from the trap by collisions was prevented by coupling the magnetron and reduced cyclotron motions by an additional r.f. field at the sum frequency of the two motions. Electronic Zeeman transitions in138Ba+and135Ba+were observed at a transition frequency of 80 GHz in a 3 Tesla B-field with a fractional uncertainty of3.10−9.From the magnetic field calibration by the cyclotron resonance of electrons stored in the same trap thegJ-factor for both isotopes could be determined to2.10−8.From radio frequency induced&Dgr;mI=1transitions in137Ba+the nuclear g-factor could be determined to5.10−6.Both measurements improve earlier results by about one order of magnitude. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57484

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Antihydrogen atoms, produced near rest, trapped in a magnetic well, and cooled to the lowest possible temperature (kinetic energy) could provide an extremely powerful tool for the search of violations of CPT and Lorentz invarianz. We describe our plans to form a significant number of cold antihydrogen atoms for comparative precision spectroscopy of hydrogen and antihydrogen. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57436

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

A theoretical study of possible signals for CPT and Lorentz violation arising in hydrogen and antihydrogen spectroscopy is described. The analysis uses a CPT- and Lorentz-violating extension of quantum electrodynamics, obtained from a general Lorentz-violating extension of the minimal standard model with both CPT-even and CPT-odd terms. Certain 1S-2S transitions and hyperfine Zeeman lines exhibit effects at leading order in small CPT-violating couplings. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57439

出版商:AIP    

年代:1999

数据来源: AIP