Buffer gas cooling, optical cycling and radiative deflection of AlF molecules

Aluminum monofluoride (AlF) is a promising candidate for a high-density magneto-optical trap (MOT) of molecules. Here, we show that AlF can be produced efficiently in a bright, pulsed cryogenic buffer gas beam, and demonstrate rapid optical cycling on the Q rotational lines of the A¹Π↔X¹Σ⁺ transition. We measure the brightness of the molecular beam to be >10¹² molecules per steradian per pulse in a single rotational state and present a new method to determine its velocity distribution accurately in a single molecular pulse. The photon scattering rate is measured using three different methods and compared to theoretical predictions of the optical Bloch equations and a rate equation model. An exceptionally high scattering rate of up to 42(7) x 10⁶ s^-1 can be sustained despite the large number of Zeeman sublevels (up to 216 for the Q(4) transition) involved in the optical cycle. We demonstrate that losses from the optical cycle due to vibrational branching to X¹Σ⁺, v=1 can be addressed efficiently with a repump laser, allowing us to scatter about 10⁴ photons using two lasers. Further, we investigate two other loss channels, photo-ionization and parity mixing by stray electric fields. The upper bounds for these effects are sufficiently low to allow loading the molecules into a MOT.