Improved Slotted Disk Type Velocity Selector for Molecular Beams

A slotted disk type mechanical velocity selector, 10 cm long and 16 cm in diameter, consisting of six disks has been constructed and tested. The velocity resolution corresponding to the half‐intensity width is 0.047; no velocity sidebands are transmitted. The effective fractional open time to the incident beam is 0.35. At the highest rotor speed used (17 000 rpm) the transmitted velocity is 1.05×105 cm/sec. A general theoretical analysis of the transmission and resolution of selectors with disks of finite thickness is presented. The velocity distribution is reported for a molecular beam effusing from an oven equipped with Zacharias corrugated foil exit canals.