European XFEL Science Seminar

Watching and directing electrons on the atomic level to understand quantum dynamics from attoseconds to femtoseconds, and beyond

by Prof. Thomas Pfeifer (Max Planck Institute for Nuclear Physics, Heidelberg)

via Zoom

via Zoom


Electrons are not only the lightest (known) fundamental particles, they are also responsible for virtually anything we see: From tiny objects under the microscope to the screen or paper we just look at, all the way and far out into the universe. Interactions with electrons also hold atoms together in molecules and electron motion is at the heart of any chemical reaction on earth, our bodies and in outer space.  Observing, understanding, and directing electron motion is thus a core topic in physics and chemistry alike, with substantial impact and relevance to other fields of science and technology.

An ongoing world-wide revolution of high-frequency (XUV and x-ray) light-source development and detection techniques keeps unlocking access to such electron motion, down to their natural time scale of attoseconds.  Moreover, the extreme intensity of current free-electron lasers (FELs) allows not only the observation of fundamental quantum dynamics in atoms and molecules, but to actively steer their motion on the fundamental electronic level.

Here in this talk, I will highlight our science mission towards building a bottom-up understanding of electron dynamics in intense external fields, starting at the level of isolated atoms featuring only a nucleus and two (correlated) electrons (e.g. in Helium), and working our way up into multi-electron atoms (e.g. neon) and polyatomic molecules (e.g. CH2I2 and C60).

Our experimental aim is to obtain the most complete picture of such fundamental (intense-)light–matter interaction processes, tuning from low into high intensity, by extracting multidimensional observables.  These include the detection of photons, ions and electrons in coincidence.

The results from these experiments not only shed new light on fundamental quantum processes, which are generally applicable also in larger systems (also relevant to single-shot imaging of complex molecules in intense x-ray fields), but also provide new technological tools, e.g. for pulse characterization, to further optimize the light sources themselves.  One exemplary long-term dream of this development is the 3D-printer on the atomic level: The writing of custom molecular structures and supramolecular assemblies by the full spatio-temporal control over the electromagnetic spectrum, coherently provided at high intensity from the infrared into the x-ray domain.

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Organized by

Serguei Molodtsov / Gabriella Mulá-Mathews