Isotopic enrichment of heavy ozone in the stratosphere

A mass‐independent, 3% enrichment of heavy ozone isotopes in the stratosphere can be assigned to a mechanism in which (1) short‐wavelength photodissociation of ozone produces O 2 ( ν ≥ 26) + O, (2) the O 2 ( ν ≥ 26) reacts with ground state O 2 to produce O 3 + O, and (3) each O atom recombines with O 2 to form O 3 . The overall reaction scheme, O 3 + hv + 3O 2 → 3O 3 , produces more ozone than it consumes. The dissociation channel which begins this scheme is more probable for heavy ozone than for 48 O 3 , and one of the oxygen atoms in the original O 3 is incorporated into a new O 3 . Thus this new ozone source tends to “distill” heavy oxygen atoms into the O 3 pool while depleting them from the O 2 pool. The amount of enrichment produced by this mechanism, while significant, is still too small to account for the large observed stratospheric enrichment of heavy ozone.