D. Liesen

Measurement of the ground-state lambshift of hydrogenlike uranium at the electron cooler of the ESR

X-rays are emitted with the radiative recombination of free electrons in an electron cooler of a heavyion storage ring. Due to a small width of the X-ray lines, an observation angle close to 0° and an accurate determination of the ion velocity, the ground-state Lambshift of hydrogenlike uranium (470 ± 16) eV could be measured to an accuracy of 3.4%. A re-evaluation of a measurement of the 1s1/2 Lambshift in hydrogenlike gold gave a new value of (202.3 ± 7.9) eV as compared to the former value of (212 ± 15) eV. The results are in excellent agreement with QED calculations and are more precise than any other measurements previously reported for a high-Z, hydrogenlike ion.

Spectroscopic Study of Hydrogenlike and Heliumlike Xenon Ions

Hydrogenlike and heliumlike xenon ions have been produced at GANIL. All Lyman and Balmer lines of both ions have been observed, for the first time. The energies of these lines, belonging to the heaviest ions ever studied, have been compared with detailed multi-configurational Dirac-Fock calculations.

Status and perspectives of atomic physics research at GSI: The new GSI accelerator project

A short overview on the results of atomic physics research at the storage ring ESR is given followed by a presentation of the envisioned atomic physics program at the planned new GSI facility. The proposed new GSI facility will provide highest intensities of relativistic beams of both stable and unstable heavy nuclei - up to a Lorentz factor of 24. At those relativistic velocities, the energies of optical transitions, such as for lasers.. are boosted into the X-ray region and the high-charge state ions generate electric and magnetic fields of exceptional strength. Together with high beam intensities a range of important experiments can be anticipated, for example electronic transitions in relativistic heavy-ion collisions such as dynamically induced e(+)e(-) pairs, test of quantum electrodynamics (QED) in strong fields, and ions and electrons in ultra-high intensity femtosecond laser fields

A tool for spectroscopy of super-heavy quasimolecules (Z1+Z2>137) the Bang-Hansteen scaling rule

From 90° line width analysis ofKα1 lines excited in very heavy ion-atom collisions (Z1 +Z2>137) mean impact parameters for the ionization probability are derived. The experimental mean impact parameters are shown to obey the Bang-Hansteen scaling rule¯bE(R)=C · ħv correlating the minimum momentum transferE(R)/v and the mean impact parameterb. Theoretical values of the constantC are (0.8±0.1) for 2p1/2σ excitation and (1.0±0.1) for 1sσ excitation in the rangeZ1+Z2=140–160. It is proposed to apply the scaling rule as a spectroscopic tool to study the 1sσ and 2p1/2σ levels in superheavy quasimolecules. The need of a sound theoretical base justifying the application of the scaling rule is emphasized.

Measurement of the (1s) Lamb shift of hydrogen-like krypton

The absolute energy of the Lyman- alpha 1 line of hydrogen-like krypton has been measured with an accuracy of 36 p.p.m. The ions were produced at GANIL (Caen) and the X-rays emitted in flight detected with a flat crystal spectrometer. The (1s) Lamb shift of hydrogen-like krypton has been found to be 11.95+or-0.5 eV in good agreement with theory.

Observation of hydrogenlike and heliumlike krypton spectra

Hydrogenlike and heliumliken=2→n=1 lines in Kr have been produced and studied for the first time. HydrogenlikeL y α lines have been observed and the fine structure interval has been determined. The absolute energy of the1P1,3P2,3P1 lines of heliumlike Kr have been measured and compared to Multiconfigurational Dirac-Fock Calculations.

SPARC: The Stored Particle Atomic Research Collaboration At FAIR

The future international accelerator Facility for Antiproton and Ion Research (FAIR) encompasses 4 scientific pillars containing at this time 14 approved technical proposals worked out by more than 2000 scientists from all over the world. They offer a wide range of new and challenging opportunities for atomic physics research in the realm of highly‐charged heavy ions and exotic nuclei. As one of the backbones of the Atomic, Plasma Physics and Applications (APPA) pillar, the Stored Particle Atomic Physics Research Collaboration (SPARC) has organized tasks and activities in various working groups for which we will present a concise survey on their current status.

Electron bremsstrahlung in collisions of 223 MeV/ u He-like uranium ions with gaseous targets

The bremsstrahlung process in the domain of strong Coulomb fields has been investigated for and Ar target electrons colliding with He-like uranium ions at . The differential cross sections for bremsstrahlung were measured at laboratory observation angles of , , and . Substantial discrepancies were found between the experimental cross sections and the first-order Born approximation calculations. The reported data provide a new testing ground for non-perturbative treatment of the coupling between radiation and matter in the presence of strong fields.

Ray tracing of curved-crystal X-ray optics for spectroscopy on fast ion beams

Abstract A method of ray tracing is presented which allows a detailed analysis of the X-ray line profile observed with a curved-crystal spectrometer for both a stationary or a fast X-ray source. In particular, the effect of finite dimensions of crystal and source and their interplay with a finite velocity vector of the source is discussed for Johann and Johansson spectrometers. It is shown how some parameters cause distortions and shifts of the reflection and how far they can be resolved by using a two-dimensional position-sensitive X-ray detector.

Precision tests of QED in strong fields: experiments on hydrogen- and helium-like uranium

In this contribution, we present an experimental study carried out at GSI Darmstadt devoted to investigation of quantum electrodynamical (QED) effects for the ground states in hydrogen- and helium-like uranium. In the experiment, X-ray spectra following radiative recombination of free electrons with bare and H-like uranium ions (U92+, U91+) were measured at the electron cooler of the ESR storage ring. Utilizing clean and favorable experimental conditions present at the electron cooler, we were able to obtain very accurate values for the ground-state binding energies from the observed X-ray transitions. When compared with theory, our results provide the most stringent test of bound-state QED for one- and two-electron systems in the strong-field regime.