Femtosecond pump-probe studies of dichlorine monoxide in solution

The first femtosecond pump-probe studies of ClOCl photochemistry in solution are presented. Following 266-nm photoexcitation of ClOCl dissolved in perfluorohexane, the resulting evolution in optical density is monitored at seven wavelengths ranging from 266 to 400 nm. A depletion in optical density consistent with ground-state ClOCl photolysis is observed, followed by increases in optical density at 266 and 315 urn assigned to the production of ClO and ClClO, respectively. Kinetic analysis of the temporal evolution in optical density establishes that photoproduct appearance occurs on the similar to10-ps time scale. Later time decay of the optical density at 315 nm is mirrored by a corresponding increase in optical density at 266 nm consistent with thermal decomposition of ClClO to produce ClO and Cl on the similar to100-ps time scale. The quantum yields for photoproduct formation are determined through analysis of the absolute change in optical density. This analysis establishes that the quantum yields for ClClO and ClO production are 0.4 +/- 0.1 and 0.6 +/- 0.1, respectively. Finally, the observation of ClClO production following ClOCl photoexcitation is similar to the behavior observed for chlorine dioxide (OClO) suggesting that photoisomerization is a general feature of halooxide reactivity in solution.