The temperature and density in an overexpanded jet (Ar) were mapped by the method of characteristics. The kinetics of condensation in the supersaturated gas along the central streamline was analyzed on the basis of four models, subject to previously developed thermodynamic relations which must apply during the homogeneous condensation of any supersaturated vapor. Here we report on detailed dynamic analyses of the rates of cluster growth. Each association:Anminus;1+A1rlarr2;Anwas represented either by a single stabilization step, or by a sequence of two energy removing collisions, for which kinetic parameters based on Lennardhyphen;Jones (LJ) potentials were estimated. Coupled differential rate equations (up to 192) were solved, both for cases when the heat of condensation was neglected, and when it was partially or fully distributed throughout the fluid. The distribution of cluster sizes declines exponentially, according toN(n)=Athinsp;exp(minus;an)+Bthinsp;exp(minus;bn), in agreement with generally observed distributions for monatomic species. For source pressures of 3 and 10 atm the condensation process becomes kinetically controlled within a distance downstream somewhat less than twice the aperture diameter. Our calculations indicated that after about three aperture lengths lsquo;lsquo;freezing inrsquo;rsquo; takes place if the heat of condensation is neglected. When the heat of condensation is distributed (partitioned in one of several plausible ways) freezing in is delayed beyond four aperture diameters. A modest fraction of the nascent clusters retain some of the heat of condensation and remain at a higher temperature than the ambient gas.
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