Water Interactions with Acetic Acid Layers on Ice and Graphite

• Adsorbed organic compounds modify the properties of environmental interfaces with potential implications for many Earth system processes. Here, we describe experimental studies of water interactions with acetic acid (AcOH) layers on ice and graphite surfaces at temperatures from 186 to 200 K. Hyperthermal D2O water molecules are efficiently trapped on all of the investigated surfaces, with only a minor fraction that scatters inelastically after an 80% loss of kinetic energy to surface modes. Trapped molecules desorb rapidly from both mu m-thick solid AcOH and AcOH monolayers on graphite, indicating that water has limited opportunities to form hydrogen bonds with these surfaces. In contrast, trapped water molecules bind efficiently to AcOH-covered ice and remain on the surface on the observational time scale of the experiments (60 ms). Thus, adsorbed AcOH is observed to have a significant impact on waterice surface properties and to enhance the water accommodation coefficient compared to bare ice surfaces. The mechanism for increased water uptake and the implications for atmospheric cloud processes are discussed.

Subject headings

NATURVETENSKAP  -- Kemi -- Fysikalisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Physical Chemistry (hsv//eng)

Keyword

SUPERCOOLED SULFURIC-ACID

MOLECULAR-DYNAMICS SIMULATIONS

HYDROGEN-BONDING INTERACTIONS

ELASTIC HELIUM SCATTERING

GAS-PHASE

COLLISION DYNAMICS

CARBOXYLIC-ACIDS

ORGANIC-ACIDS

NITRIC-ACID

SURFACE

Publication and Content Type

ref (subject category)

art (subject category)