Electrically guided continuous supersonic beams of polar molecules from a cryogenic buffer-gas source

In order to obtain dense samples of internally and translationally cold polar molecules, we use the method of buffer-gas cooling [1], combined with supersonic expansion. We have demonstrated that when the cryogenic buffer-gas cell is operated in a supersonic regime, molecular fluxes are hydrodynamically enhanced by up to two orders of magnitude. Meanwhile, the translational velocity profile of the output molecular beam is cooled to beyond Mach number 6 via supersonic expansion. Due to the cryogenic cell temperature, the forward velocity of the supersonic molecular beam is below $190\,$m/s. The low-field-seeking molecules in the so-produced continuous supersonic beam are selected via quadrupole electric guiding [2] and transfered to further experiments. Such high-flux guided continuous supersonic beams from a cryogenic reservoir provide a promising source of polar molecules amenable to deceleration and further cooling.\\[4pt] [1] L.D. van Buuren {\sl et al.}, Phys. Rev. Lett. \textbf{102}, 033001 (2009)\\[0pt] [2] S.A. Rangwala {\sl et al.}, Phys. Rev. A \textbf{67}, 043406 (2003)