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Published December 6, 1996 | public
Journal Article

Mechanism of chlorine dioxide photodissociation in condensed media


The photobleaching of OClO dissolved in CCl_4 was investigated by kinetic electron spin resonance spectrometry as a function of [OClO], [O_2], photon flux, irradiation wavelength (λ = 303, 365 and 436 nm) and temperature (233 K ≤ T ≤ 298 K). OClO decays non-exponentially, the apparent kinetic order increasing with conversion. The initial quantum yields of OClO disappearance Φ are larger than one under anoxic conditions, but decrease in the presence of O_2, except at 365 nm. The rates are directly proportional to the absorbed photon flux and depend weakly on temperature. Remarkably, OClO is partially regenerated after irradiation, even in fully bleached solid samples. We show that a minimal mechanism comprising 21 pseudo-elementary steps can account for these observations, within experimental error, if the primary products of OClO photodecomposition change from (O + ClO) at 303 and 436 nm to (Cl + O_2) at 365 nm. The photolysis of ClOClO_2, one of the putative intermediate species, into (Cl + OClO) also contributes to the initial rates at 303 nm.

Additional Information

© 1996 Elsevier Science S.A. Received 12 December 1995; accepted 29 February 1996. This project was financially supported by CONICET/Argentina under grant PID 1131/91. L.J.P. is a research staff member of CIC/Pcia. de Buenos Aires. A.J.C. is now at the Department of Physical Chemistry, Faculty of Exact and Natural Sciences, University of Buenos Aires.

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