The characteristics of a commonly used pulsed valve for the production
of free jets and molecular beams are analyzed in detail. Special atte
ntion is paid to the formation of gas pulses providing a quasisteady f
low during a certain time interval within the pulse duration, and to t
he estimation of a scaling parameter (effective diameter) for the desc
ription of the flow field. The adequacy of this effective diameter is
checked by performing time-of-flight measurements on molecular beams o
f Ne, N-2, and CH4, and stimulated Raman spectra on free jets of N-2 a
nd CH4. (C) 1995 American Institute of Physics.