Attoseconds & Picometer: Atomic-Scale Dynamics in Matter

Atomic-scale rearrangements are essential for understanding the behavior and function of molecules and advanced materials. All macroscopic changes involve local rearrangement of the atoms and electron density, which define the fundamental mechanisms of the change. The length and time scales of nuclear motions are picometer and femtoseconds; electrons can move as fast as within attoseconds. A combined, four-dimensional approach with both temporal and spatial resolution is therefore essential for capturing the action all at once.

Ultrafast Electron Diffraction and Imaging

The techniques of ultrafast electron diffraction and microscopy allow to "make a movie" of atomic-scale movements, by simultaneously providing picometer resolution and femtosecond timing. A laser pulse is used to initiate the dynamics, and ultrashort electron pulses are diffracted to visualize the atomic-scale structures as they evolve. Ultrafast diffraction results in four-dimensional information including space and time. The approach is therefore ideal for visualizing the many complicated ultrafast transitions that do not proceed directly from the initial to the final conformation, but rather follow complex non-equilibrium reaction pathways. The materials that we investigate include molecular crystals, surface adsorbates, nanostructures, charge-transfer compounds, photonic devices, eventually biomolecules, and many more.

Down to Attoseconds: Observation of Electrons Dynamics

Femtosecond resolution is perfect for observing atoms, but the motion of electrons is expected to involve times as short as attoseconds. In principle, ultrafast electron diffraction is capable of accessing this time scale, because the de Broglie wavelength of our electrons supports pulse durations of one attosecond and less. Our route into this regime is based on the compression of single-electron packets in synthesized electrical and optical fields. In contrast to spectroscopic approaches with optical pulses, attosecond electron pulses, once realized, may offer direct four-dimensional visualization of charge density dynamics with combined spatial and temporal resolution. Attosecond electron diffraction will be a free space approach with very monochromatic beams, which will allow us to investigate the motions of electron density in a large variety of complex systems, such as nonlinear optical materials, photonic devices, molecular crystals, superconductors, and many others.

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For further information, please have a look at some relevant publications.

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News:

We have open postdoc positions in ultrafast electron microscopy.

The electron microscope can now measure electromagnetic waveforms. See also the interview at Welt der Physik (in German).

We now compress and control our electron pulses with terahertz radiation. See also the press release and movie!

We could achieve 5-fs laser-electron synchronization recently.

What happens deep inside of future's ultimate electronics? This is to be recorded in space and time by Dr. Peter Baum and his team, funded with two million € via an ERC Consolidator Grant.

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