Group Seminar at MPQ: Electric-field-controlled dipolar collisions between cold and trapped polyatomic molecules
Florian Jung, Quantum Dynamics Division MPQ
Group Seminar at MPQ lecture hall and zoom
Tuesday, March 21st, 09:00am (MEZ)
Polar symmetric top molecules exhibit a permanent electric dipole moment which creates strong anisotropic interactions, and allows them to be manipulated with moderate electric fields. This, together with their multitude of internal states, renders them promising for applications in e.g. quantum information processing or cold chemistry. For these applications reaching high-density lowtemperature ensembles is imperative. This requires the capability to control collisional losses, which is a challenging task.
By combining a cryogenic buffer-gas cell with a centrifuge decelerator and an electrostatic trap, we can now confine up to 2 × 10^7 CH3F molecules at a temperature of ∼350 mK for several seconds, achieving densities of up to 10^7/cm^3, which allows for the observation of collisions . We employ a homogeneous control field, covering a large fraction of our trap to mitigate collisional losses and obtain inelastic loss coefficients below 4 × 10^−8 cm^3/s. An ab-initio theory shows excellent agreement with our experiment and highlights dipolar relaxation as the major loss mechanism. These findings are immediately relevant for cold molecular collision studies and an important step towards the observation of thermalisation between polyatomic molecules. At the moment, opto-electrical Sisyphus cooling  is being implemented in our set-up to extend the study of polyatomic molecule collisions towards ultracold temperatures.
 M. Koller et al., Phys. Rev. Lett. 128, 203401 (2022).
 M. Zeppenfeld et al., Nature 491, 570-573 (2012).