Progress towards the creation of an ultracold RbYb mixture

H. X. Yang, Jin Cao, Zhen Su +3 more

In recent years, there has been notable progress in the preparation and control of ultracold gases of diatomic molecules. The next experimental challenge is the production of ultracold polyatomic molecular gases. Here, we report the creation of an ultracold gas of 23 Na 40 K 2 triatomic molecules from a mixture of ground-state sodium-23–potassium-40 ( 23 Na 40 K) molecules and potassium-40 ( 40 K) atoms. The triatomic molecules were created by adiabatic magneto-association through an atom–diatomic molecule Feshbach resonance. We obtained clear evidence for the creation of triatomic molecules by directly detecting them using radio-frequency dissociation. Approximately 4000 triatomic molecules with a high-peak phase-space density of 0.05 could be created. The ultracold triatomic molecules can serve as a launchpad to probe the three-body potential energy surface and may be used to prepare quantum degenerate triatomic molecular gases.

Jongchul Mun, Sung Jong Park, Jiho Noh +3 more

Dajun Wang, Fudong Wang, Xiaoke Li +4 more

Cristian Bruni, Axel Görlitz

We report on the creation of ultracold heteronuclear and electronically excited Rb*Yb molecules in a hybrid conservative trap by photoassociation of ultracold $^{87}\mathrm{Rb}$ and $^{176}\mathrm{Yb}$. The molecules are formed below the ${\mathrm{Rb}}_{5\mathit{p}1}(^{2}P_{1/2})+{\mathrm{Yb}}_{6\mathit{s}2}(^{1}S_{0})$ dissociation limit and the resonances are detected using trap-loss spectroscopy. By addressing vibrational levels with binding energies down to ${E}_{B}=\ensuremath{-}h\ifmmode\times\else\texttimes\fi{}2.2\phantom{\rule{0.16em}{0ex}}\mathrm{THz}$, we study the change in hyperfine coupling of the diatomic molecule as a function of internuclear separation. We observe a decreasing hyperfine splitting for more tightly bound excited molecular states where the hyperfine splitting is reduced by more than $30%$ compared to the atomic value for $^{87}\mathrm{Rb}$.

Dajun Wang, C. Ashbaugh, Edward E. Eyler +2 more

Mateusz Borkowski, Piotr Szymon Żuchowski, R. Ciuryło +7 more

We model the binding energies of rovibrational levels of the RbYb molecule using experimental data from two-color photoassociation spectroscopy in mixtures of ultracold ${}^{87}$Rb with various Yb isotopes. The model uses a theoretical potential based on state-of-the-art ab initio potentials, further improved by least-squares fitting to the experimental data. We have fixed the number of bound states supported by the potential curve, so that the model is mass scaled, that is, it accurately describes the bound-state energies for all measured isotopic combinations. Such a model enables an accurate prediction of the $s$-wave scattering lengths of all isotopic combinations of the RbYb system. The reduced mass range is broad enough to cover the full scattering lengths range from $\ensuremath{-}\ensuremath{\infty}$ to $+\ensuremath{\infty}$. For example, the ${}^{87}$Rb${}^{174}$Yb system is characterized by a large positive scattering length of $+880(120)$ a.u., while ${}^{87}$Rb${}^{173}$Yb has $a=\ensuremath{-}626(88)$ a.u. On the other hand ${}^{87}$Rb${}^{170}$Yb has a very small scattering length of $\ensuremath{-}11.5(2.5)$ a.u. confirmed by the pair's extremely low thermalization rate. For isotopic combinations including ${}^{85}$Rb the variation of the interspecies scattering lengths is much smoother ranging from $+39.0(1.6)$ a.u. for ${}^{85}$Rb${}^{176}$Yb to $+230(12)$ a.u. in the case of ${}^{85}$Rb${}^{168}$Yb. Hyperfine corrections to these scattering lengths are also given. We further complement the fitted potential with interaction parameters calculated from alternative methods. The recommended value of the van der Waals coefficient is ${C}_{6}=2837(13)$ a.u. agrees with but is more precise than the current state-of-the-art theoretical predictions [M. S. Safronova, S. G. Porsev, and C. W. Clark, Phys. Rev. Lett. 109, 230802 (2012)].