Observation of resonant dipolar collisions in ultracold 23Na 87Rb rotational mixtures

We report the investigation on dipolar collisions in rotational state mixtures of ultracold bosonic (NaRb)-Na-23-Rb- 87 molecules. The large resonant dipole-dipole interaction between molecules in rotational states of opposite parities brings about significant modifications to their collisions, even when an electric field is not present. In this work, this effect is revealed by measuring the dramatically enhanced two-body loss rate constants in the mixtures. In addition, the dipolar interaction strength can be tuned by preparing the NaRb mixture in different rotational levels with microwave spectroscopy. When the rotational level combination is not of the lowest energy, contributions from hyperfine changing collisions are also observed. Our measured loss rate constants are in good agreement with a quantum close-coupling calculation, which we also present in full detail.

Automated summary

Our investigation focuses on dipolar collisions in rotational state mixtures of ultracold bosonic (NaRb)-Na-23-Rb-87 molecules, where the resonant dipole-dipole interaction is found to significantly modify collisions even in the absence of an electric field. We reveal this effect by measuring enhanced two-body loss rate constants in the mixtures, and demonstrate that the dipolar interaction strength can be tuned with microwave spectroscopy. Additionally, observations of contributions from hyperfine changing collisions are made when the rotational level combination is not of the lowest energy.