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E u r o s c i c o n C o n f e r e n c e o n
Physical Chemistry and
Analytical Separation Techniques
October 08-09 , 2018
Amsterdam, Nether l ands
Journal of Organic & Inorganic Chemistry
ISSN: 2472-1123
Physical Chemistry and Analytical Separation Techniques 2018
M
olecular oxygen O
2
is the most important molecule on earth’s atmosphere and stratospheric ozone O
3
protects us from the UV
radiation. The abundance of
16
O being 99.8%, O
2
and O
3
exclusively formed from it are dominant, thereby giving a reference
for any process involving oxygen. A strong enrichment of O
3
(~10%) in both
18
O and
17
O (mass-independent fractionation-MIF)
has been observed decades ago and was reproduced in laboratory experiments. Although this phenomenon remains globally
unexplained, the three-body recombination O + O
2
+ M ―
>
O
3
+ M is believed to be the main process leading to this enrichment.
At sufficiently low pressures, it can be partitioned into two steps: the formation of O3 in a highly excited rovibrational state, from
reaction O + O
2
―
>
O
3
* (step 1), and its subsequent stabilization by collision with an energy absorbing partner M (say N
2
), O
3
* + M
―
>
O
3
+ M (step 2). Thus, the efficiency of the exchange reaction O + O
2
―
>
O
3
* ―
>
O
2
+ O, involving O
3
* as an intermediate, is one
of the key parameters to understand ozone formation. We have shown that this reaction, initiated by step 1, is very fast with three
identical 16O atoms involved due to a quantum permutation symmetry effect. Consequently, it competes ferociously with step
2 described above, the latter becoming in this way much less effective. We have reproduced experimentally observed negative
temperature dependence for this reaction rate constant when
18
O is involved, along with other groups. We will sum up results
of a computationally intensive full-quantum investigation of the dynamics of the 16O +
32
O
2
,
18
O +
32
O
2
and
17
O +
32
O
2
processes
supported by an accurate global potential energy surface for the O
3
ground state. Our study based on a time independent quantum
mechanical approach demonstrates that all approximate theoretical simulation techniques and calculations previously reported
for this process result in considerable inaccuracies, especially because of the neglect of the quantum symmetries such as the
nuclear spin symmetry due to the three (or two) identical atoms,
16
O or
18
O.
pascal.honvault@univ-fcomte.frPascal Honvault and Gregoire Guillon
Laboratoire ICB- CNRS/Université de Bourgogne Franche-Comté, France
J Org Inorg Chem 2018 Volume: 4
DOI: 10.21767/2472-1123-C6-018
Quantum rate coefficients for the O + O2
exchange reaction