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Coherent electron dynamics & dephasing in isolated molecules and molecular nanoarchitectures
- Probing electron dynamics in molecular systems.
The investigation of ultrafast electron dynamics in molecules has so far been restricted by the lack of few-fs / sub-fs UV /XUV pulses for pump / probe experiments. The development of these sources and new technologies in target preparation and target characterization open the door for a new timescale in molecular physics and nanoscale science.
Here we aim at studying and — in the long run — controlling electron wavepacket motion on molecular length scales and on time scales where the nuclear coordinates are frozen. The studies hold promise of gaining unprecedented insight into intra- as well as inter-molecular charge and energy transport and electronic dephasing in molecules placed in different environments, with ramifications for molecular electronics, molecular magnetism, bionanotechnology and bioinformatics. With waveform-controlled few-cycle uv/vuv pulses (
A.1.2) it will be possible to launch an electron wavepacket at a specific site of a molecule with sub-fs timing precision, control its subsequent motion with a tailored field of the excitation pulse and monitor it by attosecond photoelectron spectroscopy (Fig. C.1.4.1).
How do the motion and decay of the wavepacket occur in isolated molecules and how can electrons propagate in molecular nano-assemblies and devices? How is their energy eventually dissipated? How do dephasing and energy dissipation depend on the environment? How can the dynamics be steered with controlled light fields? To address these questions, we shall tackle experiments on isolated molecules in the gas phase and subsequently extend attosecond electron control and spectroscopy to supramolecular architectures on surfaces.
- Example of a supramolecular system: the amino acid L-methionine and its self-assembly into a biomolecular nanograting.
Carefully selected and designed organic species and metal centres will be assembled on atomically clean substrates, where noncovalent interactions (notably hydrogen bonding and metal-ligand bonding) mediate the formation of supramolecular architectures (Fig. C.1.4.2). This allows fabrication of an intriguing variety of 1, 2 and 3D nanostructures including well-defined clusters, metal-organic arrays, nanogratings or nanoporous networks. Supramolecular engineering will create many possibilities for new device concepts. Photoswitchable molecules or molecular wires will be incorporated in nanoscale environments to achieve functional architectures for information processing. Specifically, these nanoscale environments include periodic porous systems or mesoporous materials with adjustable pore diameters, pore topology and overall morphology. Colloidal suspensions or optically clear, oriented thin films of such porous materials will be developed as nanostructured periodic hosts for the photoswitchable molecules and wires. Molecule-based magnets such as giant spin systems will be arranged on surfaces in a controlled way, for prototype single-molecule magnetic memory elements.