Relative formation rates of O-50(3) and O-52(3) in O-16-O-18 mixtures

Tunable diode laser (TDL) and mass spectrometry have been combined to measu re relative formation rate coefficients of each of the four channels contri buting to ozone of mass 50 u and 52 u produced in O-16-O-18 mixtures. Only one channel has a large rate coefficient advantage causing almost exclusive ly the observed isotope enrichment. Collisions to form ozone are end-on rea ctions. Molecular symmetry plays no apparent role in the ozone isotope enri chment process, regardless, whether or not ozone is produced in collisions with homo- or heteronuclear molecular oxygen. The oxygen isotope exchange p rocess may hold a key in explaining the rate coefficient results. (C) 1999 American Institute of Physics. [S0021-9606(99)02940-2].