Theoretical Study on the Angular Distribution of Molecular Flux Effusing into a Vacuum.

Abstract

The angular distributions of molecular flux effusing from cylindrical nozzles into a vacuum are calculated for both argon and nitrogen gas by using the Monte Carlo direct simulation method. For argon gas, the dependence of the angular distribution on the Knudsen number Kn and the nozzle length-to-diameter ratio shows a good agreement with experimental data. Both Monte Carlo and experimental data are summarized into a best-fit equation. The inelastic collision between diatomic molecules makes the peak of the angular distribution lower than that of monatomic gas for Kn < 0. 1.