Studies at the Liquid-Air Interface

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The liquid-air interface comprises many natural systems including atmospheric processes such as heterogeneous cloud formation and ozone depletion. Our group has recently characterized the following systems:
Glycerol/Water surfaces
Water at the surface of H₂SO₄/H₂O binary systems
Water at the surface of H₂SO₄/H₂O and Cs₂SO₄/H₂O binary systems
Molecular HCl at a liquid surface
Water on the surface of nitric acid solutions
Water on the surface of inorganic salts
Molecular ammonia on the surface of water
The thermodynamic properties of water mixtures are also widely studied because equilibria between aqueous- and gas-phase species at liquid surfaces are relevant to industrial applications and atmospheric systems. Indeed, the predominant components of atmospheric aerosols and droplets are sulfates, nitrates, ammonia, and water, all of which are in chemical equilibrium with the surrounding air.

Mass transfer of species into aerosol droplets has been investigated to better understand the role ammonia, HCl, and inorganic acids play in atmospheric, heterogeneous processes. Uptake of ammonia, for example, is believed to occur by molecular diffusion towards a droplet surface, followed by penetration of the air/water interface, hydrolysis, and diffusion into the bulk liquid. Typical experiments deduce the mass accommodation coefficient, of species from the gas phase into water droplets to describe processes occurring on atmospheric aerosols. An important missing component of the accommodation picture is determination of the surface structure of mixtures characteristic of atmospheric droplets. Surface structure information is invaluable for understanding aerosol neutralization pathways and aerosol growth processes. Because of the surface specificity of SFG, it is ideally suited for investigating the structure of such liquid surfaces.

  © 2001 Shultz Research Group
Last Updated: 3/4/04