Vapor Phase Homogeneous and Ion Induced Nucleation

Nucleation is one of the most ubiquitous and important phenomena in science and technology. It plays a central role in materials science, crystal growth, chemical processing, atmospheric science and cosmochemistry. This research area is of increasing importance to atmospheric chemistry, polar stratospheric clouds, acid rain and air pollution.

We have reported studies of the homogeneous nucleation behavior of non-polar normal-alkanes, including corresponding states analysis of all recent nucleation data on the n-alkanes. We have studied hydrogen bonding systems. We have also reported the first study of the homogeneous nucleation of highly polar liquids This study has demonstrated the failure of the classical nucleation theory and introduced new models for dipole alignments in clusters.

We are currently developing a new technique for the study of nucleation on well-defined ions. The method is based on Resonance Enhanced Multiphoton Ionization (REMPI), in which well-defined molecular ions act as nucleation centers for the condensation of supersaturated vapors. These experiments allow, for the first time, to selectively and unambiguously generate specific ions of interest and study their nucleating behaviors during the condensation of supersaturated vapors. We are developing this method as an ultra sensitive amplifier and detector for the chemical analysis of aerosol particles.

Our research is conducted primarily with upward thermal diffusion cloud chambers, but we are currently upgrading a fast piston-expansion cloud chamber for further research.