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Content archived on 2024-04-19

Chemistry of halogen oxides in the stratosphere


The aim of this project is to obtain a quantitative understanding of the chemical and photochemical processes involving halogen oxide species which are implicated in ozone depletion in the stratosphere, specially in the polar regions and at mid-latitudes.

The novel chemical schemes associated with this ozone destruction suggest the important role of species such as Cl0, Cl202, 0Cl0, Br0 through a number of reactions, the kinetics and mechanisms of which are not well established. Measurements of rate coefficients, product branching ratios and photochemical parameters are all involved and will be essentially made at low temperatures. The following topics will be covered:

1. Formation and decomposition of the Cl0 DIMER:
low temperature, low pressure kinetic data for the Cl0 + Cl0 + M reaction and kinetic parameters for the thermal and photolytic decomposition reactions of Cl202.

2. Coupling reactions of X0 and R02 radicals:
kinetic and mechanistic data for the reaction Cl0 + Cl0, Cl0 + CH302 and Br0 + H02.

3. Other relevant reactions:
kinetic and mechanistic data for the X + 02 + M association reactions (X = F,Br) and radical reactions involving Cl0x species.

4. Spectroscopic studies:
UV absorption cross sections of Br0, Br0N02, H0Br, Cl03 and IR spectra of Cl202, Cl203.
All these measurements are expected to be achieved through a combination of complementary experimental methods at the different laboratories to ensure high quality and reliability in the data produced. These data will be of first importance for the models both in their interpretation of field measurements and in their predictive capabilities for future ozone depletion.


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Avenue de la Recherche Scientifique 1 C

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Participants (7)