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The Ion Trap Group


New student projects available!

Have a look at our Master and Bachelor projects and join the group!

Direct frequency-comb driven Raman transitions in the THz range.

We recently used a femtosecond frequency comb to coherently drive stimulated Raman transitions between THz-spaced energy levels in a single Ca+ ion. We achieved Rabi oscillations with a contrast of 99.3% and a coherence time of milliseconds! We also showed that the population dynamics of frequency-comb-driven Raman transitions can be fully predicted from the spectral properties of the comb. These results were published in Physical Review Letters.

New Cryogenic Trap in Aarhus!

We recently trapped a few hundreds Ca+ ions in our new linear Paul trap that is placed in a cryogenic environment with 4-5K temperature! We are now running the first characterization of the trap and will soon trap Ba+ ions in order to sympathetically cool heavier molecules!

New labs

The Ion Trap Group has recently completed its move into new lab spaces. The first ions in the new labs have already been trapped! 

Here is a time lapse video of our main room during the move.

Rotational buffer gas cooling of Coulomb crystallized molecular ions. 

The Ion Trap Group has in collaboration with the Max-Planck-Institut für Kernphysik (MPIK), Heidelberg, Germany, carried out the first helium buffer gas cooling experiments on molecular ions sympathetically cooled into a Coulomb crystal. The applied method constitutes a novel route to form cold and spatially localized molecular ions. The results open up for refined studies of molecules and molecular processes in a size-range spanning from the smallest diatomic molecular ions to complex molecules of biological relevance. In terms of science, the results are expected to have impact on such diverse fields as fundamental physics investigations, high-resolution spectroscopy of complex molecules, cold chemistry, astrochemistry, as well as biochemistry. See article in Nature.

Rotational buffer gas cooling of Coulomb crystallized molecular ions

Single-ion recycling reactions.

Ion reaction rates and reaction product branching ratios have been determined through repeated regeneration of an original target ion by photodissociation after each reaction. The results have been published in Angewandte Chemie

For the first time EIT as well as all-optical EIT-based light switching using ion Coulomb crystals situated in an optical cavity has been demonstrated. The results are published in Nature Photonics:

Molecular ions for the first time cooled to their lowest vibrational and rotational level using laser-based schemes. See article in Nature Physics.

Research on the cover page of Nature Physics:


The Ion Trap Group has been and is funded by variety of funding agencies including the Danish National Research Foundation, the Ministry of Higher Education and Science, the Carlsberg Foundation, the Lundbeck Foundation, the Villum Foundation as well as the EU Commission.