Mixing of 0${}^{+}$ and 0${}^{-}$ observed in hyperfine and Zeeman structure of ultracold Rb${}_2$ molecules

Abstract

We study the combination of hyperfine and Zeeman structure in the spin-orbit coupled $A^1{\Sigma }_u^{+}-b^3{\Pi }_u$ complex of ${}^{87}{\text{Rb}}_2$. For this purpose, absorption spectroscopy at a magnetic field around $B=1000\text{G}$ is carried out. We drive optical dipole transitions from the lowest rotational state of an ultracold Feshbach molecule to various vibrational levels with $0^{+}$ symmetry of the $A-b$ complex. In contrast to previous measurements with rotationally excited alkali-dimers, we do not observe equal spacings of the hyperfine levels. In addition, the spectra vary substantially for different vibrational quantum numbers, and exhibit large splittings of up to $160\text{MHz}$, unexpected for $0^{+}$ states. The level structure is explained to be a result of the repulsion between the states $0^{+}$ and $0^{-}$ of $b^3{\Pi }_u$, coupled via hyperfine and Zeeman interactions. In general, $0^{-}$ and $0^{+}$ have a spin-orbit induced energy spacing $\Delta$, that is different for the individual vibrational states. From each measured spectrum we are able to extract $\Delta$, which otherwise is not easily accessible in conventional spectroscopy schemes. We obtain values of $\Delta$ in the range of $\pm 100\text{GHz}$ which can be described by coupled channel calculations if a spin-orbit coupling is introduced that is different for $0^{-}$ and $0^{+}$ of $b^3{\Pi }_u$.

24 pages, 7 figures

References in corpus (2)

• Hyperfine, rotational, and vibrational structure of the triplet ground state of Rb molecules
• Optimized production of ultracold ground-state molecules: Stabilization employing potentials with ion-pair character and strong spin-orbit coupling

Cited by in corpus (4)

• High Resolution Molecular Spectroscopy for Producing Ultracold Absolute Ground-State ${}^{23}$Na${}^{87}$Rb Molecules
• Magnetic quantum number resolved state-to-state chemistry
• Energy-scaling of the product state distribution for three-body recombination of ultracold atoms
• Level structure of deeply bound levels of the $c^3{\Sigma }_g^{+}$ state of ${}^{87}{\text{Rb}}_2$