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

Paper SS2-TuM10
A Combined Droplet Train / Photoemission Spectroscopy Experiment for the Investigation of Heterogeneous Reactions on Liquid Surfaces

Tuesday, November 14, 2006, 11:00 am, Room 2004

Session: Water-Surface Interactions
Presenter: D.E. Starr, Lawrence Berkeley National Laboratory
Authors: D.E. Starr, Lawrence Berkeley National Laboratory
K.R. Wilson, Lawrence Berkeley National Laboratory
H. Bluhm, Lawrence Berkeley National Laboratory
Correspondent: Click to Email
The properties of liquid/vapor interfaces strongly influence the abundance and reactivity of trace gas molecules that are important for many heterogeneous processes in atmospheric and environmental chemistry. A direct measurement of the liquid/vapor interface under atmospherically and environmentally relevant conditions is difficult due to the lack of quantitative experimental techniques that are surface-sensitive, chemically specific and can operate at elevated pressures in the Torr range. Here we describe a novel experimental setup that is operating at beamline 11.0.2 at the Advanced Light Source in Berkeley. The instrument combines synchrotron-based ambient pressure photoemission spectroscopy (APPES, operating at pressures of more than 5 Torr) and a liquid droplet train produced by a vibrating orifice aerosol generator (VOAG). In a VOAG, droplets of uniform size (5-100 Î@micron@) are generated by forcing the liquid under investigation through a vibrating orifice. The short time (milliseconds) between the generation of the droplets at the vibrating orifice and their measurement in the spectrometer minimizes the level of contamination of the surface. Beam damage is kept at a minimum since each droplet is irradiated only for a few microseconds by the incident X-rays. In addition, the interaction time of the droplet surface with gas molecules can be varied over a range from about 1 to 20 ms, allowing for measurements of the reaction kinetics at liquid surfaces as a function of exposure time to a gaseous environment. Studies of the role of liquid surface species in the transport of gas molecules across the liquid/vapor interface, as well as studies of surface-mediated chemical reactions at the liquid/vapor interface are also possible.