Intercombination-line photoassociation spectroscopy of ${}^{87}\mathrm{Rb}{}^{170}\mathrm{Yb}$

We report on the observation of photoassociation (PA) near the $\text{[Rb]}5s{}^{2}S_{\frac{1}{2}}+\text{[Yb]}6s6p{}^{3}P_1$ asymptote in a mixture of ${}^{87}\mathrm{Rb}$ and ${}^{170}\mathrm{Yb}$. In a search spanning binding energies between 0.1 and 11 GHz, a single pair of interspecies PA resonances is detected around 3.1 GHz. These resonances are characterized by extracting PA rates, binding energies, and Zeeman shift coefficients. Using one of these resonances, two-photon photoassociation is performed, improving on previous measurements of the binding energies of the two least bound states in the electronic ground state and demonstrating intercombination-line photoassociation as a powerful spectroscopic tool. We discuss implications for pathways towards RbYb molecules in the absolute ground state.

Figure 1

Schematic diagram of the relevant ground- and excited-state potentials of RbYb and the free-bound (${\mathrm{L}}_1$) and bound-bound (${\mathrm{L}}_2$) transitions used in this work.

Figure 2

Free-bound photoassociation lines observed in the Yb atom number. The solid line is a Gaussian fit as a guide to the eye.

Figure 3

Decay curves for (a) Yb and (b) Rb with the PA light on and off resonance for the stronger transition located at $-3057\text{MHz}$.

Figure 4

Investigation of the Zeeman shift of the observed transitions. (a) Spectra at various magnetic fields, offset by the magnetic field strength. (b) Reconstructed shift of A and B from Gaussian fits shown in (a).

Figure 5

Observation of two-photon photoassociation resonances (a) by scanning the bound-bound laser with the free-bound laser locked on resonance and (b) by scanning the free-bound laser while the bound-bound laser is locked on resonance (dark-resonance configuration). The energy levels on the sketches on the left-hand side are labeled with $|1\rangle$ for the scattering state, $|2\rangle$ for the bound state in the electronic ground state, and $|3\rangle$ for the electronically excited state. The scattering state and the vibrational ground state are separated with the binding energy $E_{\text{B}}$ and the thermal energy $E_{\text{therm}}$.