Under suitable conditions, partial condensation of particles can be achieved during the generation of molecular beams with a Laval nozzle, leading to an unusual increase in beam intensity in a high vacuum. The relative half-value width of the velocity distribution of a condensed argon beam, measured with a transit-time method, turns out to be less than 5 its upper limit is set only by the resolution of the measuring apparatus. The rise in the velocity of the condensed beam with intake pressure indicates that at least a part of the heat of condensation is converted to ordered mechanical energy in the nozzle. Author
Trans. of Zeitschrift fuer Physik (West Germany) v146 n2 p333-338 1956, by William J. Grimes.