EXCITED-STATE PHOTOREACTIONS OF CHLORINE DIOXIDE IN WATER

The primary photochemical processes of electronically excited OClO in water are studied at room temperature. Excitation of the 2A2 <-- B-2(1) absorption band at 355 nm leads to both photochemical dissociation and isomerization, yielding ClO + O and ClOO, respectively. The isomerized ClOO is unstable in water and thermally dissociates into Cl and O2. A Kinetic model is developed to quantify the partitioning between these two competitive processes. Comparison between experimental and simulated transient absorption data shows that 90% of the electronically excited molecules dissociate; the remaining 10% undergo isomerization to form ClOO. In addition, the simulated kinetics show that the thermal decomposition of ClOO in water has a rate constant of 6.7 x 10(9) s-1.