Spectroscopy and Photochemistry of Chlorine Dioxide

The photoreactivity of chlorine dioxide excited in the near ultraviolet is reexamined in this paper. The results of this study are used to evaluate the possible role that the photochemistry of OClO may play in polar ozone depletion. – The study reported here involves high resolution spectroscopic and photofragment experiments of isolated gas phase OClO and of OClO clustered with water. The results show that excitation in the near ultraviolet of the A(2A2) ← X(2B1) transition leads to both dissociation to form vibrationally excited ClO and O, and to rearrangement which ultimately leads to Cl and O2. Formation of Cl and O2 may contribute to catalytic polar ozone depletion. The mechanism and quantum yield for these two photoreactions are discussed. The quantum yields for the two excited state reactions are very sensitive to perturbations by intermolecular interactions. The heterogeneous photoreactivity of OClO is probed in (H2O)n clusters.