Photochemistry of the Ozone Hole:ltraviolet Absorption Cross Sections of ClOOCl and Their Temperature Effects
Date Issued
2009
Date
2009
Author(s)
Lin, Wei-Yen
Abstract
Chlorine peroxide (ClOOCl) plays an important role in the formation of the Ozone Hole. The absorption cross section of ClOOCl is a key parameter for determining the polar ozone loss rate. Conventionally, scientists determine the absorption cross sections by photo-absorption method. But all synthesized gas-phase ClOOCl samples contain impurities. Thus, there are large discrepancies in the absorption cross sections of ClOOCl. The new data published by Pope et al. [J. Phys. Chem. A 111, 4322 (2007)] are much smaller than previously accepted values. If Pope’s data are correct, about half of the observed ozone loss can not be explained. Unlike other groups, we measured the attenuation of ClOOCl molecular beam after laser irradiation by a mass detector. Therefore impurities would not contribute to the signal of ClOOCl. We determined the absorption cross sections of ClOOCl at 248, 308, 351 nm unambiguously. The cross sections we measured are much lager than Pope et al.’s data. Using our results, the current atmospheric model can well explain the observed ozone loss and concentrations of ClO and ClOOCl. Our results indicate the current model for the ozone loss is still valid. In addition, we can measure the temperature dependences of the absorption cross section of ClOOCl due to good precision of this method. This work is the first measurement for temperature effects of the absorption cross sections of ClOOCl.
Subjects
Ozone Hole
ClOOCl
absorption cross section
molecular beam
temperature dependence
Type
thesis
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