Speakers
Description
Cryogenic buffer gas sources are an essential precursor for many experiments with ultracold matter, and the relative brightness of these sources determines their scientific applications. Many interesting molecules are produced in situ, by laser ablation of a metal target followed by reaction with a gas. The understanding of the complex formation processes is currently limited. We compare, in the same experimental setup, molecular beams of the laser-coolable monofluorides AlF, CaF, YbF and MgF, and compare with theoretical modelling of the reaction dynamics (see poster by Liu et al.).
The modelling suggests that production of the closed-shell molecule AlF is one order of magnitude more efficient than for the free radical CaF, and that Al reacts more efficiently to produce AlF when NF$_3$, rather than SF$_6$, is used as the donor gas.
In the experiment, we measured the brightness of atomic Al, Ca and Yb atomic beams and compared it to AlF, CaF, YbF, and MgF molecular beams. For AlF, we also studied the phase-space distribution of the source by velocity filtering with a Stark decelerator. We find that the AlF beam has a similar brightness to the atomic Al beam, but that the other free radical molecules are an order of magnitude lower in brightness when compared to their respective atomic beams. From this we conclude that AlF is produced with an efficiency near unity, and that free radicals are generally produced with much lower efficiency than closed-shell molecules. We also find, consistent with the theoretical work, that SF$_6$ tends to result in a faster molecular beam. These findings have implications for the design of future molecular sources.
