Multi‐isotope study of ozone: Implications for the heavy ozone anomaly

Laboratory experiments have been performed with O and O₂ in their ground electronic states to study the distribution of all possible ozone isotopes formed. Results show that with respect to ⁴⁸O₃ the two symmetric molecules ¹⁷O¹⁷O¹⁷O and ¹⁸O¹⁸O¹⁸O are depleted, in good agreement with standard recombination theory. A large enrichment of about 18% is found in the asymmetric molecule ¹⁶O¹⁷O¹⁸O, while all others carry about 2/3 of that. A comparison with past laboratory and stratospheric ozone isotope measurements leads to the following conclusion: There is a standard enrichment which resides in asymmetric molecules only. It will lead to an enrichment of stratospheric ⁴⁹O₃ and ⁵⁰O₃ of 8 to 9%; this has been actually observed in recent balloon experiments. Occasionally, the enrichments in the stratosphere are larger, reaching 40% at certain altitudes. Only when ozone was formed in an electric discharge process have larger enrichments been measured in laboratory experiments, affecting both symmetric and asymmetric molecules. The results provide an important connection between numerous laboratory studies and stratospheric measurements.