The C(P-3) + O-2((3)sigma(-)(g)) -> CO2 CO((1)sigma(+)) + O(D-1)/O(P-3) reaction: thermal and vibrational relaxation rates from 15 K to 20 000 K

Author(s)
Juan Carlos San Vicente Veliz, Debasish Koner, Max Schwilk, Raymond J. Bemish, Markus Meuwly
Abstract

Thermal rates for the C(P-3) + O-2((3)sigma(-)(g)) CO((1)sigma(+))+ O(D-1)/O(P-3) reaction are investigated over a wide temperature range based on quasi classical trajectory (QCT) simulations on 3-dimensional, reactive potential energy surfaces (PESs) for the (1)A ', (2)(1)A ', (1)A '', (3)A ' and (3)A '' states. These five states are the energetically low-lying states of CO2 and their PESs are computed at the MRCISD+Q/aug-cc-pVTZ level of theory using a state-average CASSCF reference wave function. Analysis of the different electronic states for the CO2 -> CO + O dissociation channel rationalizes the topography of this region of the PESs. The forward rates from QCT simulations match measurements between 15 K and 295 K whereas the equilibrium constant determined from the forward and reverse rates is consistent with that derived from statistical mechanics at high temperature. Vibrational relaxation, O + CO(nu = 1,2) -> O + CO(nu = 0), is found to involve both, non-reactive and reactive processes. The contact time required for vibrational relaxation to take place is tau >= 150 fs for non-reacting and tau >= 330 fs for reacting (oxygen atom exchange) trajectories and the two processes are shown to probe different parts of the global potential energy surface. In agreement with experiments, low collision energy reactions for the C(P-3) + O-2((3)sigma(-)(g), nu = 0) -> CO((1)sigma(+)) + O(D-1) lead to CO((1)sigma(+), nu ' = 17) with an onset at E-c similar to 0.15 eV, dominated by the (1)A ' surface with contributions from the (3)A ' surface. Finally, the barrier for the COA((1)sigma(+)) + O-B(P-3) -> COB((1)sigma(+)) + O-A(P-3) atom exchange reaction on the (3)A ' PES yields a barrier of similar to 7 kcal mol(-1) (0.300 eV), consistent with an experimentally reported value of 6.9 kcal mol(-1) (0.299 eV).

Organisation(s)
Computational Materials Physics
External organisation(s)
Universität Basel, Brown University, Air Force Research Laboratory
Journal
Physical Chemistry Chemical Physics
Volume
23
Pages
11251–11263
No. of pages
13
ISSN
1463-9076
DOI
https://doi.org/10.1039/d1cp01101d
Publication date
04-2021
Peer reviewed
Yes
Austrian Fields of Science 2012
104017 Physical chemistry, 103006 Chemical physics
Keywords
Portal url
https://ucris.univie.ac.at/portal/en/publications/the-cp3--o23sigmag--co2-co1sigma--od1op3-reaction-thermal-and-vibrational-relaxation-rates-from-15-k-to-20-000-k(06d164c4-d3e0-4e64-bb98-432b62312616).html