Pour vous authentifier, privilégiez eduGAIN / To authenticate, prefer eduGAINeu

3–7 juil. 2023
Cité des sciences et de l'Industrie, Paris
Fuseau horaire Europe/Paris

LOW TEMPERATURE QUANTUM DYNAMICS OF OXYGEN EXCHANGE REACTIONS INVOLVING 17O

4 juil. 2023, 09:04
17m
Salle Violette Brisson

Salle Violette Brisson

Contribution orale MC5 Physico-chimie des environnements atomiques et moléculaires froids et ultra froids Mini-colloques: MC05 Physico-chimie des environnements atomiques et moléculaires froids et ultra froids

Orateur

Gregoire Guillon (ICB UMR6303 CNRS/uB)

Description

Context: Molecular oxygen is peculiar of Earth’s atmosphere and the precursor of stratospheric ozone which absorbs most of the Sun UV radiations. Oxygen isotopic analysis allows one to trace back the origin of elements constituting Solar system primitive materials, like meteorites and comets. O2 and O3 formed from 16O isotope are dominant, thereby giving a reference for any process involving oxygen. A strong enrichment, about 10% greater than that following usual fractionation rules, of O3 in both 18O and 17O, the so-called mass-independent fractionation (MIF), has first been observed decades ago in primitive chondrites and stratosphere [1,2], and since reproduced in laboratory experiments [3]. However, its proper quantum mechanical explanation has never been attained. Ozone is the stabilized form of the oxygen exchange reaction O + O2 O3 O2 + O intermediate O3. The study of the latter with 17O-enriched isotopomers of O2 is thus important for a full understanding of heavy O3 formation. The 34O2 species has already been investigated in collision with He [4], in the context of buffer gas cooling and subsequent magnetic trapping allowed by its S=1 electronic spin. Furthermore, the nonzero nuclear spin of 17O, I=5/2, makes it a suitable candidate for further study at ultra-low temperatures, in the presence of a magnetic field.

Methodology: We have used a high quality ab initio potential energy surface [5] to perform computationally intensive full quantum investigation of the dynamics of this scattering process.

Results: We shall present cross sections and rate constants [6,7,8] for the 17O + 32O2,
16O + op34O2 and 17O + op34O2 reactions. We will discuss observed isotope effects, and the importance of symmetry in relation to nuclear spin and ortho-para conversions [8].

References:
[1] R. N. Clayton, L. Grossman, L. K. Mayeda ‘A component of primitive nuclear composition in carbonaceous meteorites’ Science 182 (1973) 485
[2] K. Mauersberger ‘Measurement of heavy ozone in the stratosphere’ GRL 8 (1981) 935-937
[3] M. H. Thiemens, J. E. Heidenreich, III ‘The mass-independent fractionation of oxygen: a novel isotope effect and its possible cosmochemical implications’ Science 219 (1983) 1073-1075
[4] J. Bohn ‘Cold collisions of O2 with He’ PRA 62 (2000) 032701
[5] R. Dawes, P. Lolur, A. Li, B. Jiang, H. Guo ‘Communication : An accurate global potential energy surface for the ground electronic state of ozone’ JCP 139 (2013) 201103
[6] G. Guillon, P. Honvault, ‘Quantum dynamics of the 17O + 32O2 collision process’ JPCA 120 (2016) 8254
[7] G. Guillon, P. Honvault, ‘Quantum dynamics of 16O in collision with otho- and para-17O17O’ CPL 689 (2017) 62
[8] G. Guillon, M. Lepers, P. Honvault ‘Quantum dynamics of 17O in collision with otho- and para-17O17O’ PRA 102 (2020) 012810

Affiliation de l'auteur principal Lab. ICB UMR6303 CNRS/Université de Bourgogne

Auteur principal

Gregoire Guillon (ICB UMR6303 CNRS/uB)

Co-auteurs

Maxence Lepers (ICB - Université de Bourgogne) Pascal Honvault (ICB - Université de Bourgogne)

Documents de présentation