COMPARISON OF CHLORINE DIOXIDE PHOTOCHEMISTRY IN ACETONITRILE AND WATER USING SUBPICOSECOND PUMP-PROBE SPECTROSCOPY

The photochemical reaction dynamics of chlorine dioxide (OClO) dissolv ed in water and acetonitrile are investigated using subpicosecond pump -probe spectroscopy. The spectral dynamics observed at 267 and 400 nm demonstrate that the quantum yield for geminate recombination of ClO a nd O to form OClO is reduced in acetonitrile relative to water. Howeve r, the dynamics at 800 nm are similar for both solvents consistent wit h ClOO rather than OClO being responsible for the evolution at this wa velength. The kinetics for ground-state ClOO production and decomposit ion are significantly slower in acetonitrile relative to water suggest ing that solvent-solute hydrogen bonding is important in defining the ground state reactivity of this photoproduct. (C) 1997 Elsevier Scienc e B.V.