ESR kinetic study of the photobleaching of chlorine dioxide solutions at 303, 365 and 436 nm

Initial quantum yields for the photobleaching of OClO dissolved in CCl4 at 298 K are measured by electron spin resonance spectrometry at three wavelengths, under 1 atm of either N2 or O2. Yields are unaffected at 365 nm, but increase by about 45% at 303 and 436 nm, when O2 is replaced by N2. These results, at variance with gas-phase photolysis, suggest a qualitative change in the mechanism of photofragmentation at ≈365 nm. We show that OClO solvatochromic shifts are controlled by the dynamic polarization of the medium, rather than by a modification of the energies of the states involved.