Ultracold Molecules

Deborah Jin, Jun Ye

Jun-Ren Chen, Cheng-Yang Kao, Hung-Bin Chen +1 more

Utilizing single-photon photoassociation, we have achieved ultracold rubidium molecules with a high number density that provides a new efficient approach toward molecular quantum degeneracy. A new detection mechanism for ultracold molecules utilizing inelastic atom–molecule collision is demonstrated. The resonant coupling effect on the formation of the X 1 Σ + g ground state 85 Rb 2 allows for a sufficient number of more deeply bound ultracold molecules, which induced an additional trap loss and heating of the co-existing atoms owing to the inelastic atom–molecule collision. Therefore, after the photoassociation process, the ultracold molecules can be investigated using the absorption image of the ultracold rubidium atoms mixed with the molecules in a crossed optical dipole trap. The existence of the ultracold molecules was then verified, and the amount of accumulated molecules was measured. This method detects the final produced ultracold molecules, and hence is distinct from the conventional trap loss experiment, which is used to study the association resonance. It is composed of measurements of the time evolution of an atomic cloud and a decay model, by which the number density of the ultracold 85 Rb 2 molecules in the optical trap was estimated to be >5.2 × 10 11 cm −3 .

Jessie T. Zhang, Nicholas R. Hutzler, Lee R. Liu +2 more

Meng Shao-ying

The generation of ultracold molecules has been a hot topic in cold atom-molecule physics.It is difficult to obtain ultracold molecules with laser cooling as in the atomic system,because there are more degrees of freedom in molecules,and the level structure is denser and more complicated. For the time being,the ultracold molecules are generally generated from the ultracold atoms coupled by the external fields.The stimulated Raman adiabatic passage process(STIRAP) as an effective method of generating ultracold molecules from its atomic counterparts has been widely studied.In this article,we mainly focus on the recent research progress of dynamics,adiabaticity and instability of the dark state in the atom-molecule STIRAP.

Cheng Chin, V V Flambaum, M. G. Kozlov

Ultracold molecules offer brand new opportunities to probe the variation of fundamental constants with unprecedented sensitivity. This paper summarizes theoretical background and current constraints on the variation of the fine structure constant and electron-to-proton mass ratio, as well as proposals and experimental efforts to measure the variations based on ultracold molecules. In particular, we describe two novel spectroscopic schemes on ultracold molecules that have greatly enhanced sensitivity to fundamental constants: resonant scattering near Feshbach resonances and spectroscopy on close-lying energy levels of ultracold molecules.

Silke Ospelkaus