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Wavelength-dependent isotope fractionation in visible light O3 photolysis and atmospheric implications

Abstract : The 17O and 18O isotope fractionation associated with photolysis of O3 in the Chappuis band was determined using a broadband light source with cutoff filters at 455, 550, and 620 nm and narrowband light sources at 530, 617, and 660 nm. The isotope effects follow a mass-dependent fractionation pattern (δ17O/δ18O = 0.53). Contrary to theoretical predictions, fractionations are negative for all wavelength ranges investigated and do not change signs at the absorption cross-section maximum. Our measurements differ from theoretical calculations by as much as 34‰ in inline image = (18J/16J − 1). The wavelength dependence is also weaker than predicted. Photo-induced fractionation is strongest when using a low-wavelength cutoff at 620 nm with inline image = −26.9(±1.4)‰. With decreasing wavelength, fractionation values diminish to inline image = −12.9(±1.3)‰ at 530 nm. Results from an atmospheric model demonstrate that visible light photolysis is the most important tropospheric sink of O3, which thus contributes about one sixth to the ozone enrichment.
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https://hal.sorbonne-universite.fr/hal-01358299
Contributor : Christof Janssen Connect in order to contact the contributor
Submitted on : Monday, November 29, 2021 - 4:59:47 PM
Last modification on : Thursday, March 17, 2022 - 10:08:24 AM

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Früchtl Marion, Janssen Christof, Taraborrelli Domenico, Gromov Sergey, Röckmann Thomas. Wavelength-dependent isotope fractionation in visible light O3 photolysis and atmospheric implications. Geophysical Research Letters, American Geophysical Union, 2015, ⟨10.1002/2015GL066219⟩. ⟨hal-01358299⟩

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