Observation of resonant dipolar collisions in ultracold $^{23}$Na$^{87}$Rb rotational mixtures

TL;DR

This study demonstrates resonant dipolar collisions in ultracold NaRb molecules, revealing enhanced loss rates due to dipole interactions and showing how these can be tuned via rotational states, with results matching quantum calculations.

Contribution

It provides the first experimental observation of resonant dipolar collisions in ultracold NaRb molecules and details how to control these interactions through rotational state preparation.

Findings

Enhanced two-body loss rate constants in rotational mixtures.

Dipolar interaction strength tunable by microwave spectroscopy.

Good agreement between measured loss rates and quantum calculations.

Abstract

We report the investigation on dipolar collisions in rotational state mixtures of ultracold bosonic $^{23}$Na$^{87}$Rb 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.