Ultrafast Dynamics

Ultrafast dynamics of electrons in matter can be initiated and monitored by modern light sources, based on one ultrashort pulse and a second longer and more intese one, whose phase gets imprinted in the ionized electron (streaking), or on pump-probe schemes with two short pulses. Photon wavelengths are available from the midinfrared over the standard 800nm down to soft and hard X-rays with 1 Angstrom wavelength at X-ray free electron lasers. We have concentrated on fundamental mechanisms of light-matter coupling for single electrons "Low-energy structure" and on absorption and distribution of photons by large but semi-homogeneous finite systems, pristine or composite clusters. We also aim at developing new concepts to better describe such phenomena theoretically.

Intense field phenomena
. Ultrafast Phenomena . Dynamics induced by X-ray bursts

Ultracold Dynamics

Ultracold coherent dynamics of matter has become experimentally accessible with trapping techniques and the creation of Bose Einstein Condensates, with thousands of atoms represented by a single quantum state. As in the ultrafast our primary interest is devoted to excitation dynamics. Rydberg excitations go particlularly well along with ultracold matter since the (fragile) large Rydberg orbits survive for a long time in an ultracold environment which also is suitable to distinguish tiny energy differences between Rydberg levels.
Peculiar large Rydberg molecules can form, and the ultrastrong interaction of Rydberg atoms leads to strongly correlated gases interesting for condensed matter and to excitonic Rydberg dynamics entangling coherently atomic and eletronic motion which represents a new kind of Rydberg chemistry. The latter is particularly interesting since it can serve as laboratory to study dynamics relevant for light harvesting and even more fundamental molecular mechanisms such as conical intersections as we have shown. Moreover, Rydberg aggregates are a natural probe for coherence and can be coupled in a controlled way to different environments in order to get a better understanding of the different decoherence mechanisms. This also includes the coupling to nano-mechanical devices.

Rydberg Molecules . Excitonic Rydberg dynamics . Optomechanical Rydberg Physics


One of our long-term goals is to formulate novel concepts for a better theoretical description of excitations dynamics in the ultracold and ultrafast. Our present projects concern

The dominant interaction Hamiltonian  The envelope Hamiltonian Orientation recovery for diffuse X-ray images


Research driven by intellectual interest and serendipity -

Sports on dialysis - Remarkably, small-scale physical activity improves the health status of dialysis patients significantly. Even more surprising and delightful for a phycicist: this improvement follows a universal behavior which can be characterized by the logistic equation...

Time in quantum mechanics

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