The Nucleation of Supersaturated Vapors

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The goal of this research is to provide a better understanding of nucleation processes, and to allow us to make accurate quantitative predictions. The research will be in three somewhat different but complementary fields of investigation: ion induced nucleation, nucleation of metal vapors, and homogeneous nucleation. The P. I. has developed a new method for measuring the ion induced nucleation rate in which all the important variables (supersaturation, temperature, and ion density) are accurately known and all can be readily changed. Initial measurements on n-nonane and 1-hexanol will be repeated to decrease their uncertainty, optimize conditions and extend them to a wider range of supersaturations and to several temperatures. Studies of more complex substances such as those with quadropole moments or high polarizabilities (e.g. CS2, CC14) will also be made. A second major focus will be the homogenous nucleation of metal vapors. Metals in their dilute vapor state are nonmetallic, resulting in a cluster size dependence of the nonmetal transition. Nucleation studies of metals not only will enable one to study this phenomena at temperatures far below the critical temperature (and thus at temperatures where the change in density is essentially discontinuous), but also will test the validity of nucleation theories on a class of substances very different from any studied until now. The focus will be a joint effort of this research group and a research group at Phillips University in Marburg, Germany headed by Prof. F. Hensel and Dr. H. Uchtmann. A third focus will be continued efforts on understanding homogeneous nucleation processes. This will include studies on various substances over a wide range of rates, 10-6 to 101 nuclei cm-3 s-1. Phase change form vapor to the liquid phase by nucleation plays a key role in a wide variety.