Stratospheric ozone (O3) Is formed initially when an oxygen molecule (o2) absorbs shortwave radiation, which splits it into two oxygen atoms (O) each atom then combines with another oxygen molecule to form ozone. Usually,phorochemical reaction catalyzed by the NOx gases remove ozone at a rate equal to the rate of its formation, Chlorine catalytic cycles, which are growing rapidly in Importance in the atmosphere, disturb this natural balance and result in a net ozone loss [ see box on page 31].