Dimer Concentrations in Supersonic Free Jets

Abstract

Measurements have been made of the concentration of dimers produced during the expansion from a supersonic nozzle. The gases studied were: Ar, N2,O2, CO, CO2, C2H4, and N2O. It is shown that an effective specific heat ratio of the expanding gas offers a means of correlating the dimer concentration in terms of the source gas pressure and temperature. The two nozzles employed had opening diameters of 0.14 mm and 0.065 mm. An attempt to obtain a universal dependence for all gases in terms of reduced source parameters was partially successful. Source temperature was varied between 90 °K and 295 °K.

A mass and time-of-flight spectroscopy study of the formation of clusters in free-jet expansions of normal D2

“…For the other extreme case q = 1, the terminal dimer mole fraction is dominated by dimer formation during the free-jet expansion and the initial concentration of dimers is negligible. The available data for terminal dimer concentrations in free-jet expansions of rare gases 28,29,71,72 are correlated satisfactorily by q = 0.4 ͑Refs. 33 and 34͒ indicating that both thermodynamics and kinetics play a role.…”

“…25 and 26͒ clusters has also been investigated. Several criteria have been developed for correlating the onset of condensation 27,28 and several nucleation models have been proposed which provide empirical estimates of terminal cluster concentrations for specific cases. 3,6,[29][30][31][32] Hagena and Obert 31 were the first to develop scaling laws to predict the onset of clustering and for correlating the size of the clusters.…”

Nitrogen Condensation in a Sonic Orifice Expansion Flow

“…(3) becomes Vo-< K . /A *> < Na6> (4) where <Na^ > is the expectation value of the product. One notes from Eq.…”

High Resolution Scattering of He Atoms and D₂ Molecules from the LiF(001) Crystal Surface

“…Several criteria were developed for correlating the onset of condensation [208,209] and different nucleation models have been proposed which provide empirical estimates of dimer concentrations for specific cases [210,211]. Gordon et al adapted a recombination model suggested by Bunker in order to predict terminal dimer concentrations [3].…”