Analysis and control of doped helium droplets

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The aim of the planned research project is to combine the two fields coherent control and helium droplet research by applying optimally shaped laser pulses on the doped helium droplets. This opens interesting perspectives since it provides access to steer the photoinduced dynamics of van der Waals systems in the finite superfluid helium environment. The influence of the helium matrix on the molecular dynamics will thereby closely be examined, particularly regarding its superfluid properties, bubble dynamics, cage effects, relaxation processes, and decoherence properties. Particularly, photoassocitation of binary reactions starting from van der Waals clusters will be investigated. Polarization shaped laser pulses will then be employed to optimally steer the system to a covalently bound target state. This dynamics will be examined for helium-alkali atom exciplex formation with several attached helium atoms, for conversion of high spin alkali dimers and trimers to low spin configurations on helium droplets, and for transitions of more complex van der Waals systems to covalently bound species. Moreover, possible peptide bond formation will be investigated by starting from amino acid complexes. Another major goal will be to examine the molecular dynamics of ionic complexes in helium droplets. Thereto, we first ionize the dopant via electron collisions and then photoexcite and possibly further ionize the emerging ions with laser pulses. Particularly, molecules with structural motifs similar to fullerenes like triphenylenes and coronenes will be investigated due to their astrophysical relevance. Clusters of these molecules embedded in helium droplets will be converted by electron collisions and photoexcitation to covalently bound polycyclic aromatic hydrocarbon systems.