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

New measurements of the angular distributions of effusive gas beams emanating from two collimating tube sources are presented. These sources are a single 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, H2, N2, CO2 and C2H2) over a broad range of driving pressures. The profiles were obtained by rotating the ionization gauge gas detector about the centre of the exit of the tube. The data were acquired as a function of the gas flow rate and pressure in the source line. Comparisons of the present measurements with other experimental work and models are made.