Title: Quantum chemical and statistical rate investigation of the CF2(a(3)B(1))+NO(X-2 Pi) reaction: A fast chemical quenching process
Authors: Nguyen, Thanh Lam
Carl, Shaun
Nguyen, Minh Tho
Peeters, Jozef # ×
Issue Date: Jul-2007
Series Title: Journal of Physical Chemistry A vol:111 issue:29 pages:6628-6636
Conference: date:Univ Louvain, Dept Chem, B-3001 Louvain, Belgium
Abstract: The reaction of CF2(a(3)B(1)) with NO(X-2 Pi) was theoretically investigated using the B3LYP, MP2, CCSD(T), G2M, CASSCF, and CASPT2 quantum chemical methods with various basis sets including 6-31G(d), 6-311G(d), 6-311+G(3df), cc-pVDZ, and cc-pVTZ. In agreement with the experimental kinetic data, the CF2(a(3)B(1)) + NO(X-2 Pi) reaction is found to proceed via a fast, barrier-free combination. This process, occurring on the doublet potential energy surface, leads to the electronically excited adduct F2C-NO(2(2)A' '), which readily undergoes a surface hopping to the 1(2)A' electronic surface, with a Landau-Zener transition probability estimated to be close to 90% per C-N vibration. The metastable adduct F2C-NO(1(2)A') can then either spontaneously decompose into CF2(X(1)A(1)) + NO(X-2 Pi) in a direct chemical quenching mechanism or relax to its ground-state equilibrium structure F2CNO(X(2)A'). The product distribution resulting from the latter, chemically activated intermediate was evaluated by solution of the master equation (ME), under different reaction conditions, using the exact stochastic simulation method; microcanonical rate constants were computed using Rice-Ramsperger-Kassel-Marcus (RRKM) theory, based on the potential energy surfaces (PESs) constructed using both G2M and CASPT2 methods. The RRKM/ME analysis reveals that the hot F2CNO(X(2)A') rapidly fragments almost exclusively to the same products as above, CF2(X(1)A(1)) + NO(X-2 Pi), which amounts to an indirect chemical quenching mechanism. The reaction on the quartet PES is unlikely to be significant except at very high temperatures. The high crossing probability (up to 90%) between the two "avoided" doublet PESs points out the inherent difficulty in treating chemically activated reactions with fast-moving nuclei within the Born-Oppenheimer approximation.
ISSN: 1089-5639
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Quantum Chemistry and Physical Chemistry Section
Chemistry - miscellaneous
× corresponding author
# (joint) last author

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