SAMOP 2023 – scientific programme

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MO: Fachverband Molekülphysik

MO 1: Cold Molecules (joint session MO/Q)

MO 1.4: Talk

Monday, March 6, 2023, 11:45–12:00, F102

Ortho ground state preparation of cooled and trapped formaldehyde molecules — •Maximilian Löw, Martin Ibrügger, Martin Zeppenfeld, and Gerhard Rempe — Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching

Methods to directly cool polar molecules to ultracold temperatures saw remarkable progress in recent years. One of the most promising techniques in this field is optoelectrical Sisyphus cooling which can provide a large number of electrically trapped molecules at the sub-millikelvin level [1]. However, molecules in their absolute ground state cannot be addressed with this approach.

Cold ground state molecules can still be created by first applying Sisyphus cooling to, e.g., formaldehyde (H₂CO) molecules in the rotational states |J=3,K_a=3,K_c=0> and |4,3,1>. Then, we use optical pumping to transfer them via a vibrational transition to their ortho ground state |1,1,0>. In a proof-of-principle experiment trapped ground state molecules with a temperature of 65 mK and trapping times of several seconds were obtained. There is no fundamental obstacle to achieving lower temperatures in the future.

As formaldehyde in this state is stable against inelastic two-body collisions this fulfills an important requirement for evaporative or sympathetic cooling of this species in, e.g., a microwave trap which takes one a step closer to the long-term goal of quantum degeneracy.

[1] A. Prehn et al., Phys. Rev. Lett. 116, 063005 (2016).