Of all the water on the Earth, about 0.1 % of water constitutes clouds. What’s the big deal? Well, the surface area of the drops in the clouds (assuming spheres of 5 micron diameter) exceeds the surface area of the Earth by a factor of 50!! Thus, it is important to understand chemical and physical phenomena that manifest at the air-water interface, e.g. interactions of gases such as NOx, SOx, O3 with the surface of water drops and marine aerosol. We are investigating acid-base reactions, specific-ion effects, catalysis, ocean-atmosphere exchange, and interactions of atmospheric gases with surfaces coated with aqueous layers—most things on our planet! To probe the air-water interface, we carry out collisions between gases and water droplets and measure rates, chemical intermediates, and products formed ‘ on-water’ via mass spectrometry.
A. J. Colussi (Caltech), M. R. Hoffmann (Caltech), Shinichi Enami (U Kyoto)