PHYS 635 |
| The kinetics of the heterogeneous reaction between gas-phase ozone and chlorophyll present at the air-water interface are altered in the presence of actinic radiation . Glancing-angle laser-induced fluorescence measurements of the surface concentration of chlorophyll were used to study the kinetics of this reaction, which display a Langmuir-Hinshelwood mechanism under all conditions except for salt solutions of high enough pH. In this case there is a large enhancement in the rate and a change to a linear dependence on ozone concentration when the solution is illuminated with actinic light. The wavelength dependence of this enhancement was studied, using a series of long-pass filters. The full spectrum of light promoted the greatest increase in rate; wavelengths of light between 350 and 715 nm also increase the rate significantly but are slightly slower than a reaction run under the full spectrum. When the illumination was restricted to wavelengths above ~800 nm the mechanism reverted to that seen in darkness. We will present these results, as well as measurements of the excitation spectra of chlorophyll at the aqueous surface, which may help to explain this behavior. |
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PHYS Poster Session - Physical Chemistry of Atmospheric Processes
7:30 PM-10:00 PM, Wednesday, April 9, 2008 Morial Convention Center -- Hall A, Poster
Sci-Mix
Division of Physical Chemistry |