Electrostatic Extraction of Cold Molecules from a Cryogenic Reservoir

We present a method which delivers a continuous, high-density beam of slow and internally cold polar molecules. In our source, warm molecules are first cooled by collisions with a cryogenic helium buffer gas. Cold molecules are then extracted by means of an electrostatic quadrupole guide. For ND(3) the source produces fluxes up to (7 +/-(7)(4))x10(10) molecules/s with peak densities up to (1.0 +/-(1.0)(0.6))x10(9) molecules/cm(3). For H(2)CO the population of rovibrational states is monitored by depletion spectroscopy, resulting in single-state populations up to (82 +/- 10)%.