Hydrogenic Lamb shift in Ge31+ and the fine-structure Lamb shift

Using x-ray diffraction and beam-foil spectroscopy, we have determined precise wavelengths for Lyman alpha(1) and Lyman alpha(2) in hydrogenic germanium of 1.166 993 8 +/- 33 +/- 169 and 1.172 433 6 +/- 39 +/- 170 angstrom. Hydrogenic germanium Ge31+ 1s-2p(3/2) and 1s-2p(1/2) Lamb shifts are measured to be 66 080 +/- 237 +/- 1121 and 67 169 +/- 281 +/- 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 397 617 +/- 251 +/- 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.