Ab initio derived analytical fits of the two lowest triplet potential energy surfaces and theoretical rate constants for the N(4S)+NO(X 2Π) system

Abstract

Articles you may be interested inThe lowest doublet and quartet potential energy surfaces involved in the N ( 4 S)+ O 2 reaction. II. Ab initio study of the C 2v -symmetry insertion mechanism Ab initio, VTST, and QCT study of the 1 2 A ″ potential energy surface of the N ( 2 D)+ O 2 (X 3 Σ g − )→ O ( 3 P)+ NO (X 2 Π) reaction This work presents two new analytical fits of the ground potential energy surface ͑PES͒ ( 3 AЉ) and the first excited PES ( 3 AЈ) involved in the title reaction, considering the N-abstraction ͑1͒ and the O-abstraction ͑2͒ reaction channels, and the reverse reaction ͑Ϫ1͒. The PESs are derived from ab initio electronic structure calculations by means of second-order perturbation theory on a complete active-space self-consistent-field wave function ͑CASPT2 method͒. Stationary points and extensive grids of ab initio points ͑about 5600 points for the 3 AЉ PES and 4900 points for the 3 AЈ PES͒ were fitted along with some diatomic spectroscopic data to better account for the experimental exoergicity. Thermal rate constants were calculated ͑200-5000 K͒ for all mentioned reaction processes by means of the variational transition-state theory with the inclusion of a semiclassical tunneling correction. Excellent agreement with the experimental data was observed for reaction ͑1͒ and its reverse, within all the temperature range, substantially improving the results derived from previous analytical PESs. The contribution of the 3 AЈ PES to the reaction rate constant (k 1 ) was small even at high temperatures ͑e.g., only 10.8% at 2500 K͒. Moreover, the main contribution to reaction rate constant (k 2 ) was due to the 3 AЈ PES, differing from what happens for reaction ͑1͒.The O-abstraction reaction channel accounts for a 3.0% of the total reaction (kϭk 1 ϩk 2 ) at 5000 K, consistent with the very limited experimental information available.

N2, O2, NO state-to-state vibrational kinetics in hypersonic boundary layers: The problem of rescaling rate coefficients to uniform vibrational ladders

“…In reaction (12), on the 3 A 00 PES there is no energy barrier from reactants to products, whereas on the 3 A 0 PES there is a low energy barrier of 0.292 eV [22]. It follows that reaction (12) can occur only on the 3 A 00 PES at room temperature but also on the 3 A 0 PES at higher temperatures, even if this contribution should be small [23].…”

“…is more studied in literature [19][20][21][22][23][24][25][26]. Reactants and products correlate with two main PESs, the 3 A 00 , the ground potential energy surface, and the 3 A 0 , the first excited one [22].…”

“…For more details see Ref. [12] To the knowledge of the authors, the 3 A 00 and 3 A 0 PES of Gamallo et al [22,23] are the best ones available in the literature. Nevertheless some difficulties arise in the use of the first excited one.…”

“…In the present work [27,28], for the calculation of the cross sections and rate coefficients of reaction (10.b), the Gamallo et al [22] 3 A 00 and 3 A 0 PESs are used, in particular their analytical expressions [23]. The rate coefficients of reaction (10.b) are obtained by a weighted sum of the rates calculated on the 3 A 00 PES, k( 3 A 00 ), and on the 3 …”

Molecular Physics of Elementary Processes Relevant to Hypersonics: Atom-Molecule, Molecule-Molecule and Atoms-Surface Processes

“…Concerning the O + N 2 reaction, the PESs adopted are those of Ref. [27] which are believed to be the best currently available for this system. The software used for such calculations has been entirely developed by some of us [30], and then specifically adapted for distributed computations on the grid [17].…”