Large and unusual isotope effects in the three-body ozone formation reaction, O(3P)+O2→O3*+M→O3, originate from the nonstatistical behavior of metastable O3* complexes. Previous theoretical treatments of isotope-specific rate coefficients for ozone formation compared with experimental values suggest that the lifetimes of asymmetric versus symmetric O3* (e.g., 18O16O16O and 17O16O16O vs. 16O18O16O and 16O16O16O) are substantially different but the chemical physics of these differences remains mysterious. Herein we experimentally investigate the pressure and bath gas dependence of the 17O and 18O isotopic composition of O3 formed in the laboratory by photolysis of O2. Results help to clarify the role of intra- and/or inter- molecular energy redistribution in O3* in creating or diminishing the unusual heavy isotope enrichments in ozone and provide insights into the underlying chemical physics.

Bath gas and pressure dependence of the anomalous isotopic composition of ozone

253rd National Meeting (2017)

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