Dynamic electron correlations in one- and two-center atomic systems

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The structure and time evolution of matter on a microscopic scale crucially depend on electron correlations. Correlated electron dynamics is responsible for a wide variety of processes in nature, ranging from the origin of magnetism and the functionality of a helium-neon laser to the energy transfer in biomolecules. Some of the clearest manifestations of electron correlations appear in atomic systems where they can be studied in great depth due to modern experimental techniques. Reaction microscopes or ion storage rings, for example, allow for a detailed exploration of quantum processes at the microscopic scale of single atomic particles. The prospect of corresponding experiments on dynamic electron correlations in the near future calls for the development of sophisticated theoretical treatments. They shall help to correctly interpret the experimental data and to reveal the role of electron correlations in especially interesting situations: in particular, when atomic electrons are (i) subject to extreme high-field environments or (ii) located at two different sites which, either, are almost at rest and separated by relatively large distances, or move at high relative velocity.In this theoretical project, our goals are twofold. First, we want to study dynamic correlations between free and deeply bound electrons which are subject to the very strong electric field of a highly charged ion. The processes of resonant electron scattering and electron-impact ionization shall be explored in detail, including relativistic correlation effects, such as the Breit interaction. Corresponding experimental studies are planned at storage-ring facilities in Europe and China. We will also address the question as to which extent electronic correlations on the microscale can be influenced and even controlled by the application of a resonant laser field.Second, we want to explore dynamic processes driven by two-center electron correlations. They arise, in particular, in large diatomic molecules bound by van-der-Waals forces. While dynamic electron correlations in such two-center systems have successfully been investigated in recent years, there exists only limited knowledge about the molecular response to incident electron beams. We aim to study photon- and electron-impact ionization of asymmetric diatomic van-der-Waals molecules, where the dominant channel is expected to rely on the dynamic correlation between electrons located at the two well-separated atomic centers. Besides, we shall also study two-center electron correlation effects in mutual ionization occurring in fast collisions of light ions with hydrogen and helium atoms, including collisions assisted by a laser field.Our results may be able to form a bridge between our understanding of one-center and two-center electron correlations and guide the way towards new experiments.