Sub-millikelvin dipolar molecules in a radio-frequency magneto-optical trap

TL;DR

This paper reports a novel magneto-optical trapping scheme for SrF molecules that achieves sub-millikelvin temperatures and significantly higher phase space densities than previous methods, enabling improved control of cold molecules.

Contribution

The authors introduce a new trapping technique that destabilizes dark states via synchronized polarization and magnetic field reversal, leading to lower temperatures and higher densities.

Findings

Achieved temperatures as low as 400 μK.

Enhanced phase space density by three orders of magnitude.

Improved trap lifetime and molecule number.

Abstract

We demonstrate a scheme for magneto-optically trapping strontium monofluoride (SrF) molecules at temperatures one order of magnitude lower and phase space densities three orders of magnitude higher than obtained previously with laser-cooled molecules. In our trap, optical dark states are destabilized by rapidly and synchronously reversing the trapping laser polarizations and the applied magnetic field gradient. The number of molecules and trap lifetime are also significantly improved from previous work by loading the trap with high laser power and then reducing the power for long-term trapping. With this procedure, temperatures as low as 400 $\mu$K are achieved.