Angular profiles of molecular beams from effusive tube sources: I. Experiment

New measurements of the angular distributions of effusive gas beams emanati ng from two collimating tube sources are presented. These sources are a sin gle tube of aspect ratio 25 and a multi-capillary array of aspect ratio 100 . The data were collected for a wide variety of gases (He, Ne, Ar, Kr, Xe, H-2, N-2, CO2 and C2H2) over a broad range of driving pressures. The profil es were obtained by rotating the ionization gauge gas detector about the ce ntre of the exit of the tube. The data were acquired as a function of the g as flow rate and pressure in the source line. Comparisons of the present me asurements with other experimental work and models are made.