The effects of finite background pressures on free supersonic jets from sonic nozzles were investigated. It was found that at sufficiently low jet densities, which were characterized in terms of nozzle Knudsen number, axial distance and background pressure level, the background gas freely invades the jet flow field. This invasion results in substantial scattering of the jet molecules with the consequence that molecular beams extracted from such jets suffer a marked attenuation of their intensity. Some possible implications with respect to previously observed species separation are discussed. Author
Subcontracted to Princeton Univ., N. J. Presented at the International Symposium (4th) on Rarefied Gas Dynamics, Univ. of Toronto, 14-17 Jul 64.