Abstract: A molecule separator comprising an evacuation chamber adapted to be connected to a vacuum pump, a pair of coaxially aligned input and output nozzles sealed within the chamber, the nozzles being formed of a single length of tubing having a transverse cut extending at least part way through the tubing so that the bore of the tubing communicates with the chamber, and means connecting the lengths of tubing on either side of the cut to maintain the cut sections of tubing in accurate axial alignment.