AVS 53rd International Symposium
    Surface Science Tuesday Sessions
       Session SS2-TuM

Paper SS2-TuM13
The Adsorption and Uptake of Acetone on Ice Studied with Ambient Pressure Photoemission Spectroscopy

Tuesday, November 14, 2006, 12:00 pm, Room 2004

Session: Water-Surface Interactions
Presenter: H. Bluhm, Lawrence Berkeley National Laboratory
Authors: D.E. Starr, Lawrence Berkeley National Laboratory
M. Ammann, Paul Scherrer Institute
H. Bluhm, Lawrence Berkeley National Laboratory
Correspondent: Click to Email
The interaction between small molecules and ice particles has broad implications in atmospheric chemistry. While many experimental techniques, such as flow tube and Knudsen cell measurements and laser based spectroscopic techniques, have provided a great deal of insight into the kinetics and mechanisms associated with these reactions, most of these techniques lack the ability to chemically identify the species directly adsorbed on the ice surface. On the other hand, surface science techniques are particularly well-suited for exactly this purpose but generally require Ultra-High Vacuum to be utilized, precluding their use under atmospherically relevant conditions where the vapor pressure of ice is in the mTorr to Torr range. With the development of synchrotron-based Ambient Pressure Photoemission Spectroscopy (APPES) the chemical identification of adsorbed molecules on the ice surface at atmospherically relevant conditions becomes possible. As an initial step in these studies we have investigated the adsorption and uptake of acetone on the ice surface. The sequestering of acetone by ice particles in the atmosphere and polar snowpack may play an important role in atmospheric chemistry due to acetoneâ?Ts role as a radical source in the upper troposphere and radical chemistry in polar snowpack. In addition, the acetone/ice system is believed to be a fairly simple, reversible adsorption system. Uptake measurements using the integrated C1s peak area as a function of acetone partial pressure indicate an adsorption energy of approximately 45 kJ/mol. In addition, high resolution C1s spectra as well as O K-edge Near Edge X-ray Absorption Fine Structure (NEXAFS) both show little to no modification of the acetone molecule or the ice surface upon adsorption. The combined results indicate a weak interaction between the acetone molecule and ice surface under ambient conditions.