Speaker
Description
We present our recent progress on laser cooling AlF molecules using deep lasers. AlF is distinctively different from the molecular species that have been laser-cooled so far: it is a stable molecule that can be produced in large quantities and it has a strong $A^1\Pi\leftarrow X^1\Sigma^+$ transition near 227.5 nm that can be used for rapid slowing and cooling in a magneto-optical trap (MOT) with a large capture velocity. Similar to alkaline-earth atoms, AlF has narrow, spin-forbidden $a^3\Pi\leftarrow X^1\Sigma^+$ transitions near 367 nm for precision spectroscopy and narrow-line cooling.
Using two deep ultraviolet lasers, we demonstrate laser slowing of AlF molecules produced in a cryogenic buffer gas molecular beam. Molecules are decelerated from 150 to 70 m/s using the chirped-frequency laser slowing method. We experimentally measured the loss probability from the laser cooling scheme to the second vibrationally excited level of the $X^1\Sigma^+$ state, finding $1.8(5) \times 10^{-4}$. This implies a photon scattering limit of about 5,000 with only a single vibrational repump laser.
In addition, we present new experiments using our continuous AlF molecular beam oven. We compare the output flux of the oven to that a of supersonic beam of AlF, finding that its continuous output exceeds the peak flux of the supersonic source at around $J=7$. The continuous source is then used to measure high $(v,J)$ levels of the $c^3\Sigma^+$ state, providing new information about electronic states near the first dissociation limit of the molecule. We observe that the molecular beam, produced at a temperature near 1,000K, thermalises with the vacuum walls of our experiment and produces a transient room temperature vapour. This presents a possibility to laser cool and trap molecules from a greatly simplified and inexpensive source, in a multitude of rotational states.
