A Thermal Energy Molecular Beam Source for Use in Scattering Experiments
A new nozzle source is discussed that produces a high-intensity molecular beam with very small dispersion in velocity. When signal-to-noise ratio in scattered beam experiments is used as a measure of performance this source is shown to be approximately equal in quality to a Kantrowitz-Grey source of comparable size. Furthermore it is argued that many existing Kantrowitz-Grey sources could be operated as simple nozzle sources with no appreciable loss in performance. The present source has several new features. The beam intensity is uniform over the beam cross section. Source performance is not strongly dependent on skimmer geometry; hence, a simple collimating hole in a plate suffices. Source performance is quite insensitive to the size of the collimating hole and its distance from the nozzle; thus, they may be adjusted to tailor the size and shape of the beam to the particular application. The present source may be uniquely suitable for a proposed new method of beam collimation.