LAUSR

Abstract Ozone exhibits large and mass independent isotopic fractionations (MIF) in oxygen isotope ratios relative to molecular di-oxygen (O2) from which it is formed. An interpretation of this effect was proposed based on the behavior of the indistinguishable isotopes 16O in scattering processes. We report here an experiment aimed at testing one of the predictions of this model. O3 was formed by high frequency discharge in O2 with pressures ranging between 1.6 and 38 Torr. The isotopic evolution of the closed O2 reservoir was monitored during its distillation taking place during the continuous removal of ozone by condensation. Its composition evolves from a mass independent to a mass dependent fractionation along with the decrease in pressure. The isotopic pathways defined by this evolution in the 3 isotopes diagram are in quantitative agreement with the theoretical prediction of the disappearance of MIF with the increase of the complex lifetime stabilized as ozone.