Direct Loading of BaF Molecules with a Conveyor-Belt Magneto-optical Trap

We report the realization of a blue-detuned magneto-optical trap (BDM) of BaF molecules. The (1+1) type BDM and (1+2) type conveyor-belt MOT (CB-MOT) are explored. While the (1+1) BDM provides only a weak trapping force, the CB-MOT significantly compresses the molecular cloud, achieving a Gaussian rms width of 316 μm, a temperature of 240 μK, and a peak number density of 2.4×10^{7} cm^{-3}. This performance marks two orders of magnitude improvement over red-detuned MOTs. More importantly, we demonstrate the efficient direct loading of the CB-MOT from a slowed molecular beam, surpassing the loading efficiency of the standard dual-frequency MOT. This surprising result is attributed to the dipole-force-dominated trapping mechanism, wherein the capture velocity increases continuously with laser power, unimpeded by the saturation limit of photon scattering. This method is particularly advantageous for laser cooling and trapping challenging molecular species with large mass, small photon recoil, and narrow linewidths.