High–resolution measurements of the K-shell spectral lines of hydrogenlike and heliumlike xenon

With the implementation of a transmission-type curved crystal spectrometer at the Livermore high-energy electron beam ion trap (SuperEBIT) the window on sub-eV level measurements of the ground-state quantum electrodynamics and the two-electron quantum electrodynamics of high-Z ions has been opened. High-resolution spectroscopic measurements of the Kα spectra of hydrogenlike Xe53+ and heliumlike Xe52+ are presented. The electron-impact excitation cross sections have been determined relative to the radiative recombination cross sections. The electron-impact energy was 112 keV which is about 3.7 times the excitation threshold for the n=2→1 transitions. Although the relative uncertainties of the measured electron-impact excitation cross sections range from about 20% to 50%, significant disagreement between the measured and calculated cross section values has been found for one of the helium-like xenon lines. Overall, the comparison between experiment and theory shows that already for xenon (Z=54) the Breit in...