1) Cl2 + hv -> 2Cl* (this reation produces chlorine radicals) Cl* + O3 -> ClO* + O2 (chlorine reacts with ozone to form chlorine monoxide) O3 + hv -> O* + O2 (ozone is also photolyzed to produce atomic oxygen) ClO* + O* -> Cl* + O2 (chlorine radicals are reformed) NET: 2O3 -> 3O2 (the result is conversion of ozone to molecular oxygen)