SURFACE-TOPOLOGY OF THE ION-INDUCED VAPOR NUCLEATION RATE

Ion-induced nucleation involves additional electrostatic interactions between vapor molecules (atoms) and ions, The electrostatic force help s to form the ion stabilized prenucleation embryos and lowers the free energy barrier for nucleation. The free energy for ion-induced critic al embryos formation has been calculated using the Thomson's term in t he framework of the classical theory of nucleation. Nucleation theory has made obvious progress, but the understanding of the nucleation phe nomenon is far from complete. Some ideas for the identification of pos sible new directions to improve both homogeneous and heterogeneous nuc leation theories can be found by analyzing the topology of nucleation rate surfaces. The creation of the ion-induced nucleation rate surface s is based on the knowledge of phase state diagrams, experimental resu lts on ion-induced nucleation, and a few plausible assumptions. In thi s article the surfaces of the ion-induced nucleation rates for metasta ble vapor nucleation will be constructed, Semiempirical rules are form ulated for the ion-induced vapor nucleation based on both known experi mental and theoretical results. By using surface topology analysis, pr oblems in heterogeneous nucleation theory can be formulated more clear ly and future directions for improvements can be discussed. A point on the spinodal line was found by extrapolation of the logarithm of the actual vapor pressure for ion-induced and homogeneous nucleation at a constant nucleation rate as a function of inverse temperature. Nucleat ion rate scaling of the surface should yield a quantitative scale for the ion-induced nucleation rates, Phase diagrams need to be incorporat ed into the interpretation of experimental and theoretical results on ion-induced nucleation. (C) 1998 American Association for Aerosol Rese arch.