Contact

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Tim Schäfer
Group Leader
Phone:+49 551 201-1260
Dan Engelhart
Ultra-cold molecular beams
Phone:+49 30 84135726

Department of Dynamics at Surfaces

Surface scattering using Stark decelerated and oriented beams

Tim Schäfer leads a group focusing on Surface scattering using Stark decelerated and oriented beams with co-workers Nils Bartels, Fabian Grätz, Nils Hocke and Dan Engelhart.

Beams of oriented molecules

It is a long held dream of chemists to be able to grab the molecules by "quantum handles" and line them up in a special orientation ready to react, a phenomenon chemists call "steric influence". In this line of research, we study the effect of molecule-surface orientation on surface scattering processes. A strong electric field produced near the surface interacts with an incident molecule's electric dipole moment, allowing us to orient molecules for surface collisions. For example we may define conditions for the NO molecule relative to a Au(111) surface so that either the N atom hits first or the O atom hits first. Through sophisticated spectroscopic methods we can aim the NO molecule at the surface and test the most recent theories of non-adiabatic dynamics at surfaces.

Ultra-cold molecular beams

"Cold molecules research" is a rapidly emerging field providing fascinating new approaches to the study of molecule-surface dynamics. Our molecular decelerator slows pulses of neutral molecules to velocities below 50 m/s using strong, quickly switched electric fields. Such molecules have translational energies similar to those in the interstellar medium. Moreover their translation energy is highly defined and can be tuned. In this sense one produces well-defined matter waves that are in many ways similar to laser beams.

We prepare and detect these "cold" molecules in chosen internal quantum states using a sophisticated three-laser pump-dump-probe scheme. By observing the scattering of these molecules from cryogenically cooled surfaces, we investigate an energy regime in which quantum phenomena play a leading role in energy transfer.

 
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