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Project Progress

Co-Investigator Richard Flagan and his group reviewed approaches for quantitative measurements of the rate of homogeneous nucleation. They have built a nucleation-pulse expansion cloud chamber, illustrated in Figure 1, for this study. In this system, supersaturation sufficient to induce nucleation is produced by adiabatic expansion. This system uses adiabatic expansion to produce supersaturation in a vapor mixture, maintains that supersaturation for a fixed time interval to allow nuclei to form, and then recompresses the gas to reduce the supersaturation so the nuclei grow without additional new particle formation. Mie scattering patterns in light scattering at fixed angle are used to determine the number concentration of grown particles from which the nucleation rate is calculated. Operational testing of the apparatus is now underway. For the initial experiments, the conditions and vapors used in previous nucleation studies to enable apparatus validation before moving on to low temperature studies of tholin-related vapors.