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Abstract

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 that help to relate quite different scenarios. Understanding this multi-electron dynamics on very short time scales is vital for assessing the radiation damage inflicted and for paving the way to coherent diffraction imaging of single molecules.