A new source of ozone in the terrestrial upper atmosphere?

The simultaneous measurements of atomic O, O 2 , O 3 , and N 2 between 90 and 110 km obtained by a rocket‐borne mass spectrometer flown during the Aladdin 74 program provide an opportunity to test directly the simple atmospheric chemical model first proposed more than 50 years ago by S. Chapman, which is today the core of the complex chemistry controlling stratospheric O 3 . The Aladdin 74 O 3 results are found to be significantly in excess of model abundances computed using the most current values of the key chemical parameters. The calculations may possibly be in error due to uncertainties in these key parameters and/or in the measurement of the related species. However, the extra O 3 may be a consequence of reactions between ground state O 2 and electronically excited O 2 resulting from the recombination of atomic O.