Dynamics of photo-activated Coulomb complexes

Intense light with frequencies above typical atomic or molecular ionization potentials as provided by free-electron lasers couples many photons into extended targets such as clusters and biomolecules. This implies, in contrast to traditional multi-photon ionization, multiple single-photon absorption. Thereby, many electrons are removed from their bound states and either released or trapped if the target charge has become sufficiently large. We develop a simple model for this photo activation to study electron migration and interaction. It satisfies scaling relations which help to relate quite different scenarios. To understand this type of multi-electron dynamics on very short time scales is vital for assessing the radiation damage inflicted by that type of radiation and to pave the way for coherent diffraction imaging of single molecules.Comment: 14 pages, 6 figures, 1 tabl

Massively Parallel Ionization of Extended Atomic Systems

Massively parallel ionization of many atoms in a cluster or bio-molecule is identified as new phenomenon of light-matter interaction which becomes feasible through short and intense FEL pulses. Almost simultaneously emitted from the illuminated target the photo-electrons can have such a high density that they interact substantially even after photo-ionization. This interaction results in a characteristic electron spectrum which can be interpreted as convolution of a mean-field electron dynamics and binary electron-electron collisions. We demonstrate that this universal spectrum can be obtained analytically by summing synthetic two-body Coulomb collision events. Moreover, we propose an experiment with hydrogen clusters to observe massively parallel ionization.Comment: 4 pages, 5 figure

Phonon-assisted tunneling through quantum dot stacks

The impact of electron-phonon interaction on the coherent transport through a quantum dot stack is investigated using the nonequilibrium Green's function technique. While the main resonance is due to the alignment of the single dot levels, satellite peaks occur due to resonances with phonon replica of the bare levels. This effect is analyzed in detail and we show that the inclusion of nondiagonal self-energies leads to a significant reduction of the induced current, which is interpreted as an interference effect