I will present our recent results on laser cooling CaF molecules to below the Doppler limit. We produce the molecules in a buffer gas cell via laser ablation of Ca into a constant flow of cryogenic helium gas mixed with SF6.
The molecular pulse has a mean forward velocity of 140m/s and contains about
1.9x1011 molecules/sr/pulse in the electronic, vibrational and rotational ground state. The molecules are slowed by chirped radiation pressure slowing to about 10m/s1, captured in a magneto-optical trap and Doppler cooled to about 10mK. I will present the properties of the magneto-optical trap and compare them to analytical and numerical models and to the properties of standard atomic MOTs. We cool the molecules further to about 960µK by decreasing the intensity of the MOT beams. Finally, we load the molecules into a three-dimensional blue-detuned molasses where they cool to 50µK, well below the Doppler limit2.