UV photolysis of ClOOCl

ClOOCl (ClO dimer) photolysis is believed to dominate the catalytic destruction of polar stratospheric ozone during springtime through the production of atomic chlorine. Decomposition by an alternate pathway to form ClO would not catalyze ozone loss. Molecular beam experiments have demonstrated that photoexcitation of ClOOCl at both 248 and 308 nm leads to dissociation via multiple dynamical pathways, producing ClO + ClO and 2Cl + O-2. At 248 nm, both concerted and sequential dissociation to 2Cl + O-2 were observed. The primary dissociation channels occurred within a rotational period at both excitation wavelengths. The relative Cl:ClO product yields are 0.88:0.12 and 0.90:0.10 at 248 and 308 nm, respectively. Lower limits on these ratios were determined. These results substantially confirm the importance of ClOOCl photolysis in catalyzing springtime polar ozone depletion.