Photodissociation of the ClO dimer (ClOOCl) is studied in the ultraviolet regime (250 and 308 nm) under collision-free conditions. The primary photolysis products are probed by photoionization mass spectrometry. At both photolysis wavelengths, exclusively the formation of 2Cl + O-2 is observed, corresponding to a primary quantum yield gamma(Cl) near unity. Considering the error limit of the experimental results one obtains gamma(Cl) greater than or equal to 0.98 at 250 nm and gamma(Cl) greater than or equal to 0.90 at 308 nm, respectively. At both photolysis wavelengths the pathway yielding ClO is not observed, corresponding to gamma(ClO) less than or equal to 0.02 at 250 nm and gamma(ClO) less than or equal to 0.10 at 308 nm. Sensitivity studies of these results with respect to ozone depletion in the stratosphere regarding photochemically induced ozone loss are discussed using model simulations. These simulations suggest that a change of gamma(Cl) from 1.0 to 0.9 leads to a reduction of polar ozone loss of similar to5%.