Monomer and molecular cluster interactions illuminate nucleation processes
Abstract
Much of the ice observed in the atmosphere forms at thermodynamic conditions that make homogeneous nucleation unlikely. The resulting expectation that atmospheric ice nucleation is largely heterogeneous means that aerosol particle surfaces play an important role in ice nucleation. To complement measurements of ice nucleating particles in the atmosphere we utilize an experimental technique, an Environmental Molecular Beam (EMB), to probe fundamental molecule--surface interactions. Recent experiments with a range of surfaces including refractory, soot--like, analogues and volatile organic compounds, like nopinone a secondary organic aerosol component, demonstrate that even in idealized and rarified systems molecular clustering can quickly compete with desorption processes. The effect can be augmented on surfaces where diffusing H2O molecules have access to strong binding sites. Importantly, most classical theoretical descriptions of heterogeneous ice nucleation are limited to monomolecular adsorption and desorption and do not fully consider the kinetic effects of fast clustering. Such clustering will necessarily change the surface energetics and thus may help to explain observations of anomalous supersaturations required for deposition nucleation. The EMB technique is a special tool for molecular-level observations that when applied to these systems may illuminate paths towards better theoretical descriptions of ice nucleation.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A53O3107T
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0320 Cloud physics and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSES