Formation of water clusters in a free molecular jet of binary mixtures

Abstract

The formation process of water clusters is investigated experimentally with a supersonic free molecular jet of water vapor mixtures of Ar, Xe, N2, CO2 and CO, especially noticing the effect of the solute molecules on the cluster formation. The terminal concentrations of clusters formed through a supersonic molecular expansion are measured with a mass spectrometer by changing the mole fraction of water vapor at the source. It is observed that, in the range of relatively small H2 O mole fraction of binary mixtures at the source, the formation process of water clusters is controlled mainly by the thermodynamical effects of the expansion. On the other hand, at larger H2 O mole fractions, the molecular dynamical behavior of mixture molecules must be taken into account for understanding the formation process of water clusters. In both cases, the binary species play an important role in the formation process of water clusters.