Anomalous isotope effects in the O(1D) + CO2 isotope exchange reaction

PHYS 368

Laurence Y. Yeung, lyeung@caltech.edu1, John M. Eiler, eiler@gps.caltech.edu2, and Mitchio Okumura, mo@its.caltech.edu1. (1) Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Division of Chemistry and Chemical Engineering, MC 127-72, Pasadena, CA 91125, (2) Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd, MC 100-23, Pasadena, CA 91125
The stable isotope composition of atmospheric CO2 can be used to constrain the relative strengths of carbon sources and sinks, and trace the evolution of large-scale atmospheric transport. In the stratosphere, CO2 shows an unusual, puzzling enrichment in 17O relative to 18O which is strongly correlated with enrichments in multiply-substituted isotopologues of mass 47 (mainly 13C18O16O). We report evidence of an anomalous enrichment in the multiply-substituted CO2 isotopologues arising directly from O(1D) + CO2 isotope exchange reaction. This reaction proceeds through the CO3* intermediate and these observations may provide information on the dynamics and mechanism of the exchange process. The implications of this for the electronic structure of CO3*, symmetry-based anomalous isotope effects, and stratosphere-troposphere transport are discussed.
 

Poster Session
7:30 PM-10:00 PM, Wednesday, 13 September 2006 Moscone Center -- Hall D, Poster

Sci-Mix
8:00 PM-10:00 PM, Monday, 11 September 2006 Moscone Center -- Hall D, Sci-Mix

Division of Physical Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006