Ab initio study of the mechanism of the atmospheric reaction: NO₂ + O₃ → NO₃ + O₂

Abstract

The atmospheric reaction NO2 + O3 --> NO3 + O2 (1) has been investigated theoretically by using the MP2, G2, G2Q, QCISD, QCISD(T), CCSD(T), CASSCF, and CASPT2 methods with various basis sets. The results show that the reaction pathway can be divided in two different parts at the MP2 level of theory. At this level, the mechanism proceeds along two transition states (TS1 and TS2) separated by an intermediate, designated as A. However, when the single-reference higher correlated QCISD methodology has been employed, the minimum A and the transition state TS2 are not found on the hypersurface of potential energy, which confirms a direct reaction mechanism. Single-reference high correlated and multiconfigurational methods consistently predict the barrier height of reaction (1) to be within the range 2.5-6.1 kcal mol(-1), in reasonable agreement with experimental data. The calculated reaction enthalpy is -24.6 kcal mol(-1) and the reaction rate calculated at the highest CASPT2 level, of k = 6.9 x 10(-18) cm(3) molecule(-1) s(-1). Both results can be regarded also as accurate predictions of the methodology employed in this article.

Measurement of the 17O‐excess (Δ17O) of tropospheric ozone using a nitrite‐coated filter

“…The Δ 17 O(O 3 *) value thus obtained is relevant to other bimolecular reactions incorporating in their products the same reactive O-atom of ozone (i.e., reactions involving the same transfer mechanism as the O 3 + NO 2 reaction). [39] It is therefore highly relevant to the study of the propagation of the Δ 17 O(O 3 ) through atmospheric reactions. [21,23,40] Reagent preparation and filter coating procedure…”

Simulation of the diurnal variations of the oxygen isotope anomaly (Δ<sup>17</sup>O) of reactive atmospheric species

“…Ab initio calculations on the mechanism of the reaction NO 2 +O 3 reveal that it proceeds through the abstraction of the terminal O atom of ozone (Peìro-Garcìa and Nebot-Gil, 2003). In addition, the transfer of 17 O through reaction NO 2 +O 3 has been recently studied in the lab and it was also concluded that only the terminal O atom of ozone is transferred (Berhanu and Bhattacharya, personal communication, 2011).…”

17O excess transfer during the NO2 + O3 → NO3 + O2 reaction

“…29 Based on ab initio studies, the reaction of NO 2 with O 3 seems to be determined by the π orbital of the terminal oxygen atom of ozone. 30 Accordingly, NO 2 attacks the terminal oxygen of ozone and forms a single transition state (TS1), the rate-determining step. On the contrary, the NO + O 3 reaction proceeds through two transition states (TS1 and TS2) as well as an intermediate (A).…”

“…On the contrary, the NO + O 3 reaction proceeds through two transition states (TS1 and TS2) as well as an intermediate (A). 30,31 Application of the singlereference higher correlated quantum configuration interaction with single and double excitation methodology (QCISD) (Ref. 30) for the computation of the reaction mechanism in case of NO 2 + O 3 shows that the overall reaction is a direct process with no intermediate (A) and transition state TS2.…”