The photolysis half-life of aqueous chlorine in clear sky, summer noon sunlit (47 degrees North) water of pH 8 is 12 minutes when measured at the surface. It increases with decreasing pH due to the decreasing ratio of OCl- to HOCl to 60 minutes at pH 5.

OCl- photolyzes more rapidly at sunlight wavelengths than HOCl, probably because it absorbs much more strongly in the sunlight region (>300 nanometers). Within the wavelength region of maximum overlap with sunlight spectrum (>300 nm) OCl- exhibits a molar absorption coefficient that is 10-20 times greater than that of HOCl.

The effective wavelength region for significant sunlight absorption by aqueous chlorine is restricted to between 320 nm and 340 nm (nanometers).

The photolytic half-life of aqueous chlorine at the surface of a flat water body is about 12 minutes at pH 8 and 37 minutes at pH 7.