[en] Quantum-electrodynamic (QED) influences of strong atomic fields on the structure of highly-charged, heavy ions are investigated. A survey on the present experimental status and the recent achievements in this field is given concentrating on the heaviest few-electron systems. The experimental techniques, from the different X-ray spectroscopy techniques (nondispersive, dispersive, and absorber edge methods) via VUV spectroscopy to collision methods (like dielectronic recombination or Q-value measurements) are discussed and possible future developments and prospects are outlined

[en] Highly-charged, high-Z ions provide unique relativistic systems for atomic structure and collision studies. Typical examples for relativistic effects observed in those systems by photonic, electronic and atomic collisions will be discussed. These examples are radiative electron capture (REC), resonant transfer and excitation (RTE) and single excitation (EXC). In all these processes the complete interaction-including retardation and full multipole expansion-has to be taken into account. In contrast to non-relativistic systems the magnetic interaction plays an essential role. A review on experiments confirming these effects at moderate relativistic collision velocities is given

[en] The two-electron QED contributions to the ground state binding energy of He-like Kr(34+) ions has been determined in two independent experiments performed with electron beam ion traps (EBIT) in Heidelberg (HD) and Tokyo (BT, Belfast-Tokyo collaboration). X-rays arising from radiative recombination (RR) of free electrons to the ground state of initially bare Kr(36+) and hydrogen-like Kr(35+) ions were observed as a function of the interacting electron energy. The K edge absorption by thin Eu and W foils provided fixed photon energy references used to measure the difference in binding energy, ΔE-2e, between the H- and He-like Kr ions (35+ and 34+, respectively). The two independent measurements agree well, yielding a final result of ΔE-2e=641.8±1.7 eV. This value confirms recent theoretical results totally based on rigorous QED calculations. Its accuracy is just of the order required to access screened radiative QED contributions

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