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SUMMARY:Spectroscopic studies of the chlorine monoxide dimer (ClOOCl) - Is
 la  Young\, Centre for Atmospheric Science\, Cambridge
DTSTART:20081027T141500Z
DTEND:20081027T151500Z
UID:TALK13940@talks.cam.ac.uk
CONTACT:Dr Francis Pope
DESCRIPTION:Photolysis of the ClO dimer is recognized as the rate determin
 ing step in seasonal polar stratospheric ozone depletion. As the photolysi
 s rate of any species depends on the absorption cross section of that mole
 cule the absorption cross-section of ClOOCl must be known to high precisio
 n if atmospheric models are to accurately predict the rate of ozone deplet
 ion in polar regions. Currently the published literature suggests discrepa
 ncies exist that become noticeably more significant at the longer waveleng
 th region (>300nm). A study of  Pope et al. showed substantially smaller v
 alues for the absorption cross section of the ClO dimer than previously su
 ggested. This is important in the polar lower stratosphere where the inten
 sity of light at longer wavelengths is higher\, causing greater effects to
  ozone concentrations.\nOne possible explanation for the wide range of res
 ults is due to the difficulties in producing ClOOCl under laboratory condi
 tions. Molecular chlorine is present as an impurity in the laboratory synt
 hesis of the ClO dimer. Therefore\, it is vital to be able to subtract the
  Cl2 spectral interference from the ClO dimer spectrum. The use of broadba
 nd cavity enhanced absorption spectroscopy (BBCEAS) will allow the detecti
 on of absorption spectra over the 520-570nm wavelength range where Cl2 is 
 believed to exhibit vibrational structure in this region. This data\, toge
 ther with UV spectra detected simultaneously\, will allow the ClO dimer sp
 ectrum to be determined unambiguously by subtracting the influence of the 
 Cl2 spectrum.\n
LOCATION:Unilever Lecture Theatre\, Department of Chemistry
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