Electronic Spectra of Carbonyl Sulfide Sulfur Isotopologues

Agustín J. Colussi; Fok-Yan Leung; Michael R. Hoffmann

doi:10.1071/EN04010

RESEARCH ARTICLE

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Electronic Spectra of Carbonyl Sulfide Sulfur Isotopologues

Agustín J. Colussi ^A ^B , Fok-Yan Leung ^A and Michael R. Hoffmann ^A

+ Author Affiliations

- Author Affiliations

^A W. M. Keck Laboratories, California Institute of Technology, Pasadena, CA 91125, USA.

^B Corresponding author (e-mail: ajcoluss@caltech.edu).

Environmental Chemistry 1(1) 44-48 https://doi.org/10.1071/EN04010
Submitted: 14 March 2004 Accepted: 9 May 2004 Published: 30 June 2004

Environmental Context. Sulfate aerosols have been linked with ozone-depleting reactions, and their influence on cirrus cloud formation may affect climate. One source of sulfate aerosols is sulfur-containing gases such as carbonyl sulfide, which can rise up to the statosphere and become transformed into sulfate under the prevailing sunlight, but the importance and details of the phenomena involved are poorly understood. With a view to providing the fundamental information required to analyze the atmospheric processing of carbonyl sulfide, this paper reports the sulfur isotope effects on its ultraviolet absorption spectrum.

Abstract. Carbonyl sulfide (OCS), a relatively inert tropospheric species that photolyzes into CO + S upon reaching the stratosphere, is deemed a significant contributor to background sulfate aerosol. A recent analysis of atmospheric infrared transmittance data has revealed that OC³⁴S is preferentially depleted above ~10 km. We now report that the OC³⁴S absorption band between 200 ≤ λ [nm] ≤ 260 at 298 K is broader and more intense than its OC³²S counterpart. This finding is consistent with the faster photolysis of OC³⁴S, and with a time-dependent formulation of electronic spectra. Since OCS photolysis in the lower stratosphere occurs in a spectral range in which its absorption cross-section is unaffected by temperature, we are able to estimate a ³⁴S-enrichment factor <³⁴ϵ> ~ (67 ± 7)‰ for this process that is commensurate with the value previously inferred from OC³⁴S/OC³²S ratio versus altitude profiles.

Keywords. : atmospheric chemistry — isotopes — carbonyl sulfide — stratospheric sulfate aerosol — photodissociation

Acknowledgments

We thank Kyle Bayes and Stanley Sander (JPL), and Nathan Dalleska (Caltech) for valuable experimental assistance.

References

Electronic Spectra of Carbonyl Sulfide Sulfur Isotopologues

Acknowledgments

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