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Dynamics in charge transfer and ionization processes in fast ion-helium collisions


Schneider,  Katharina Elisabeth
Daniel Fischer - Emmy Noether Junior Research Group, Junior Research Groups, MPI for Nuclear Physics, Max Planck Society;

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Schneider, K. E. (2012). Dynamics in charge transfer and ionization processes in fast ion-helium collisions. PhD Thesis, Ruprecht-Karls-Universität, Heidelberg.

In the course of this work transfer ionization (TI), radiative electron capture (REC), and single ionization (SI) in fast ion-helium collisions have been studied. For this purpose, two experimental techniques, a 4π coincident ion-electron momentum spectrometer, namely a Reaction Microscope (REMI) and the heavy ion storage ring TSR, providing excellent beam properties, have been combined. In TI, i.e. the ejection of one plus the capture of a second target electron, the role of electronelectron correlations is of particular interest. In order to unravel different correlated as well as uncorrelated mechanisms, differential data has been recorded for different perturbations (projectile charge to speed ratio). For the first time strong evidence of a recently proposed, correlated TI process was found experimentally. In a second, pioneering experiment it has been attempted to perform the first kinematically complete measurement on REC. Here, an electron from the target is captured by the projectile simultaneously emitting a photon. In order to observe the emerging photons, a detector covering a large solid angle has been designed and implemented in the REMI. Although three particle coincidences have been recorded between recoil ions, projectile ions, and photons, experimental proof of the acquisition of REC coincidences was prevented due to limited statistics. Finally, in studies on SI, the influence of the projectile beam coherence properties on the collision dynamics has been investigated. The pronounced differences to earlier data taken with a projectile beam with much smaller coherence length provide evidence for its influence on the ionization dynamics, which is generally neglected in theoretical calculations. These results could pave the way to a final resolution of the long standing question on the origin of the discrepancies between theory and experiment in fully differential cross sections