Timing many-body processes in small quantum systems

The rapid light-source development is advancing on several frontiers. One is the quest for ever shorter light-pulses. Attosecond light-bursts enable experiments that follow the dynamics of the electrons.

Here time-resolved photoionization experiments have already revealed previously unattainable electron escape times and the possibilities to clock quantum mechanical processes is booming. The key is to get hold of both phase and amplitude of the time-dependent electronic wave-packets.

We build theoretical and computational tools for the interpretation and quantitative description of experimental observations with attosecond light sources, in close contact with experimental groups.

Our aim is to study the zoo of screening and relaxation events that are initiated when electrons are ionized from deeper energy levels.

Important questions are the duration of different processes, the relative time when secondary electrons appear in the continuum, its dependence on the coherence of the particles, and the reality of time-order in quantum mechanical systems.Another frontier concerns intensity. A number of current projects strive for extreme light fields.

Their realization will lead to a novel importance of magnetic interactions, and to electrons driven to relativistic velocities. The need for relativistic time-domain calculations is obvious.

We develop reliable and efficient methods to solve the full-dimensional time-dependent Dirac equation for atoms exposed to extreme fields.