The standard view is that solar radiation at wavelengths shorter than 242 nm photo-dissociates oxygen, and the resultant atoms form ozone by O + O2 reaction. But the atmosphere is a stew, albeit dilute, of high-energy particles. This is particularly true for oxygen.

The products of direct ozone photo- dissociation are not necessarily distinguishable from those originating with O2. Thus, ozone photo-dissociation, usually viewed as a do-nothing process in terms of changing the ozone balance, can have a significant effect in this regard, particularly because ozone photo-absorption rates are much greater than those for oxygen (Slanger, 1994). O(‘D) is quenched rapidly by all collision partners and is the single most important intermediate in the atmosphere as it generates several reactive molecules (OH, NO, and CH3) important in stratospheric chemistry. Till recently, the reactions shown in 1b, giving ground-state products have been largely ignored.

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But the active O2 molecules appear to have much impact on atmospheric chemistry in that they are copiously produced and unlike O(‘D), are not rapidly quenched by O2 and N2 (Slanger, 1994).