An experimental test for the mass independent isotopic fractionation mechanism proposed for ozone

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 16 O 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.

Mass-independent fractionation of titanium isotopes

“…As shown in Fig. 5, the calculated (20) and measured (21) x values are in reasonable agreement (m = 46 is shown as an example).…”

“…The discovery of the mass-independent isotope fractionation (MIF) of oxygen isotopes in ozone [1][2][3] has drawn considerable theoretical and experimental interest. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] However, no consensus has been yet reached in the literature about the origin of MIF. Interestingly, a similar isotopic distribution of oxygen isotopes was observed fifty years ago in the refractory minerals of the carbonaceous meteorites (usually referred to as CAIs, Calcium-and Aluminum-rich inclusions).…”

Four Isotope-Labeled Recombination Pathways of Ozone Formation

“…It was argued by several authors [10,11,38,39] that the lifetimes of metastable states in symmetric and asymmetric ozone molecules may be quite different, and this may explain the symmetry-driven η-effect. Lifetimes are inversely proportional to resonance widths, so, here, in order to check this hypothesis, will obtain the distributions of reso- 3) onto three components that correspond to the covalent well states (red), van der Waals plateau states (green), and the continuum states in the asymptotic region of the PES (blue).…”

Lifetimes and decay mechanisms of isotopically substituted ozone above the dissociation threshold: matching quantum and classical dynamics

“…Many efforts have been devoted to further theoretical modelling of the MIF processes: various possible mechanisms: classical trajectory and quantum mechanical calculations have been carried out by groups of Schinke 30,46,64,79,80 and Babikov et al 48,81–85 Other approaches have been reported in ref. 47 and 86–90, and some of them not necessarily based on the stabilisation of have been discussed in ref.…”