A status report on experimental tests of QED in medium-Z systems

1s-2p Lyman ␣ transitions in hydrogenic iron Fe 25+ have been observed from a beam-foil source in fourthorder diffraction off ADP 101 and PET 002 crystals, simultaneously with the n =2 to n = 4 Balmer ␤ transitions diffracted in first order. Calibration of the local dispersion relation of the spectrometer using Balmer ␤ lines provides measurements of Lyman ␣ wavelengths. The approach of fitting the full two-dimensional dispersion relation, including other members of Balmer and Lyman series, limits random and systematic correlation of parameters, and reveals a major systematic due to dynamical diffraction depth penetration into a curved crystal. The development of a theory of x-ray diffraction from mosaic crystals was necessary for the accurate interpretation of the experimental data. Photographic theory was also developed in the process of this research. Several systematics are discussed and quantified for the first time for these medium-Z QED comparisons. 2s-1s and 4f-2p satellites are explicitly investigated, and a dominant systematic is uncovered, which is due to the variable location of spectral emission downstream of the beam-foil target. 1s-2p 3/2 , 1s-2p 1/2 iron Lamb shifts are measured to be 35 376± 1900 cm −1 and 35 953± 1800 cm −1 . These agree with but lie higher than theory. This represents a 5.7% measurement of the hydrogenic 1s-2p 1/2 Lamb shift in iron. The technique also reports the iron 2p 3/2 -2p 1/2 fine structure as 171 108 cm −1 ± 180 cm −1 , which represents a 51% measurement of the hydrogenic iron fine-structure Lamb shift, and reports measurements of secondary lines.

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Hydrogenic Lamb shift inGe31+and the fine-structure Lamb shift

Chantler

Laming

Silver

et al. 2009

Phys. Rev. A

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Using x-ray diffraction and beam-foil spectroscopy, we have determined precise wavelengths for Lyman ␣ 1 and Lyman ␣ 2 in hydrogenic germanium of 1.166 993 8 Ϯ 33Ϯ 169 and 1.172 433 6 Ϯ 39Ϯ 170 Å. Hydrogenic germanium Ge 31+ 1s-2p 3/2 and 1s-2p 1/2 Lamb shifts are measured to be 66 080Ϯ 237Ϯ 1121 and 67 169Ϯ 281Ϯ 1237 cm −1 , respectively. This 14 ppm measurement of the wavelengths thus provides a 1.8% measurement of the 2p-1s Lamb shift and is an improvement by a factor of 3 over previous work. Fitting the full two-dimensional dispersion relation, including Balmer and Lyman series, limits random and systematic correlation of parameters. Dominant systematics are due to diffraction parameters including crystal thickness and alignment, differential Doppler shifts due to the variable location of spectral emission downstream of the beam-foil target, and dielectronic, 2s-1s, and 4f-2p satellites. Models developed are applicable to all relativistic plasma modeling in beam-foil spectroscopy at accelerators. The technique also reports the germanium 2p 3/2 -2p 1/2 fine structure as 397 617Ϯ 251Ϯ 512 cm −1 , representing a 0.14% measurement of the fine structure and a 71% measurement of the QED contribution to the hydrogenic germanium fine structure, an improvement of a factor of 6 over previous work. We also report a precise measurement of heliumlike resonances and fine structure.

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A status report on experimental tests of QED in medium-Z systems

Cited by 4 publications

References 19 publications

Ab initiodetermination of Kα line strengths and energies in transition metal atoms

Ab initiodetermination of Kα line strengths and energies in transition metal atoms

Hydrogenic Lamb shift in ironFe25+and fine-structure Lamb shift

Hydrogenic Lamb shift inGe31+and the fine-structure Lamb shift

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