Plmtolysis Products and Absorption Cross Sections of the C 1 O Dimer

Both the photolysis products and absorption of khnology cross sections of the C1O dimer, C1OOC1, are important to the photochemistry of the polar winter. In this work dimer photolysis was studied at the wavelength 254 mn, at 195 K. The dimer was prepared by the photolysis of C120 at 254 nm. As ditner appeared, it absorbed a significant fraction of the 254 nm light, By following the rate of photolysis of C120, it was possible to distinguish between possible dimer photolysis paths producing either Cl + CIOO or CIO + C1O. The results indicate that the former path predominates, in agreement with earlier literature results. Measurements ‘were also made of the dimer cross sections. The results yield somewhat lower cross sections in the longer wavelength region (>300 nm) than those obtained by previous workers. Introduction The CIO dimer is formed by the self-reaction of CIO radicals at the low temperatures of the polar winter. When sunlight is present, the dimer is thought to take part in catalytic ozone destruction by yielding chlorine atoms upon photolysis, followed by attack of the chlorine atoms on ozone. CIOOCI -t hu -+ Cl+ C1OO (1) Cloo -+ cl +“ 02 (2)