Isotopic composition of stratospheric ozone

Using recently measured rates for isotopic variants of the ozone formation reaction O + O-2 + M, we derive expressions for the enrichment of symmetric and asymmetric O-50(3) and O-49(3) in stratospheric ozone and calculate total enrichments of 123 parts per thousand and 107 parts per thousand for O-50(3) and O-49(3), respectively. We compare the calculations with measurements made with the Smithsonian Astrophysical Observatory far-infrared spectrometer during seven balloon flights Which took place between 1989 and 1997, We find that the calculations are in reasonable agreement with the average observed enrichments of 102+/-43 parts per thousand and 73+/-60 parts per thousand for O-50(3) and O-49(3), respectively, where the errors indicate the estimated accuracy; we also find that our measurements are in agreement with other recent stratospheric and tropospheric measurements. Using our measurements of the enrichment of the asymmetric and symmetric forms of O-50(3) and O-49(3), We estimate branching ratios of 0.43+/-0.03 and 0.46+/-0.06 for production of the symmetric isotopomer by the reaction of O-16 with O-34(2) and O-33(2), respectively.