Introduction

Dense and cold samples of molecules offer exciting prospects for various fields. This includes the study of chemical reactions at low temperatures, applications in quantum-information processing and quantum simulations, as well as the investigation of processes beyond the standard model, which can, e.g., cause a violation of time-reversal symmetry. Moreover, polar molecules attract a lot of interest due to their long-range, anisotropic dipole-dipole interactions. These interactions give rise to new scattering phenomena and the formation of exotic phases of quantum matter.

In contrast to atoms, molecules are intractable to laser cooling because of their complex structure. Therefore, other techniques are being pursued. In the last years our group has developed a versatile method to produce cold polar molecules: electric velocity filtering and guiding. In our laboratories, we exploit the interaction between polar molecules and an electric field created, e.g., by an electric quadrupole guide. With this field we extract the slowest molecules from a thermal ensemble and make them available for further experiments.

At present our research focuses on two main topics: the combination of buffer-gas cooling and electric guiding and the demonstration of optoelectrical cooling, a new cooling technique for molecules. Buffer-gas cooling expands the electric guiding technique to the production of molecules with a pure internal state distribution. Optoelectrical cooling combines spontaneous photon decay with strong electric field interactions to create a Sisyphus-type cooling scheme capable of reaching sub-mK temperatures.

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