Laser photolysis of ozone in the presence of ammonia. Formation and decay of vibrationally excited NH2 radicals

Cheskis, Sergey; Iogansen, A.A.; Sarkisov, O. M.; Titov, A. A.

doi:10.1016/0009-2614(85)87010-x

Cited by 9 publications

(5 citation statements)

References 9 publications

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“…Therefore, the calculation is not affected by acceleration caused by vibrational excitation of some of the produced NH 2 radicals, nor by the fact that about 5 % of the NH 2 prepared directly by photolysis of ammonia is in the 2 A 1 excited state. [12,14] Thus, the calculated activation energy is expected to be larger than that reported by IUPAC.…”

Section: Reaction Enthalpy and Barrier Heightsmentioning

confidence: 72%

“…[8±12] A number of studies have determined the rate coefficient to be within the range of 1.2 to 1.8 Â 10 À13 cm 3 molecule À1 s À1 at room temperature. [9,10,12] However, Kurasawa and Lesclaux [8] obtained a somewhat lower value, 0.63 Â 10 À13 cm 3 molecule À1 s À1 , and Patrick and Golden as much as 3.25 Â 10 À13 cm 3 molecule À1 s À1 . [11] The issue is, therefore, open and probably additional experimental measurements have to be carried out in order to yield a conclusive determination for the rate constant.…”

Section: Introductionmentioning

confidence: 96%

“…A higher activation energy has been suggested, which takes into account the acceleration of Reaction (3), which is caused by vibrational excitation of some of the NH 2 radicals, and the fact that about 5 % of the NH 2 prepared directly by ammonia photolysis is in the 1 2 A 1 excited state. [12,14] In this paper, theoretical results of the mechanism of Reaction (3) derived from a high-level ab initio computation are presented. Theoretical and computational details are described in Section 2.…”

Section: Introductionmentioning

confidence: 99%

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An Ab Initio Study on the Mechanism of the Atmospheric Reaction NH₂+O₃→H₂NO+O₂

2003

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The atmospheric reaction NH2 + O3-->H2NO + O2 has been investigated theoretically by using MP2, QCISD, QCISD(T), CCSD(T), CASSCF, and CASPT2 methods with various basis sets. At the MP2 level of theory, the hypersurface of the potential energy (HPES) shows a two step reaction mechanism. Therefore, the mechanism proceeds along two transition states (TS1 and TS2), separated by an intermediate designated as Int. However, when the single-reference higher correlated QCISD and the multiconfigurational CASSCF methodologies have been employed, the minimum structure Int and TS2 are not found on the HPES, which thus confirms a direct reaction mechanism. Single-reference high correlated and multiconfigurational methods consistently predict the barrier height of the reaction to be within the range of 3.9 to 6.6 kcal mol-1, which is somewhat higher than the experimental value. The calculated reaction enthalpy is -67.7 kcal mol-1.

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Section: Reaction Enthalpy and Barrier Heightsmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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An Ab Initio Study on the Mechanism of the Atmospheric Reaction NH₂+O₃→H₂NO+O₂

2003

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“…Nevertheless, we expect higher values for this calculated magnitude because: The same IUPAC recommends also 2.0 kcal mol −1 for the well‐known OH + O 3 reaction, when the experimental studies of Back and Yokota 31 and Hack et al29 have proven that the reactivity of NH 2 radicals is significantly lower. We are studying NH 2 in its 1 2 B 1 (v = 0) ground state. Thus, the acceleration caused by vibrational excitation of some of the NH 2 radicals is not included 30 Five percent of the NH 2 prepared directly by NH 3 photolysis is in the 2 A 1 excited state.…”

Section: Resultsmentioning

confidence: 99%

“…We are studying NH 2 in its 1 2 B 1 (v = 0) ground state. Thus, the acceleration caused by vibrational excitation of some of the NH 2 radicals is not included 30…”

Section: Resultsmentioning

confidence: 99%

A theoretical ab initio study on the H₂NO + O₃ reaction

2003

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The deviation of the NH(2) pseudo-first-order decay Arrhenius plots of the NH(2) + O(3) reaction at high ozone pressures measured by experimentalists, has been attributed to the regeneration of NH(2) radicals due to the subsequent reactions of the products of this reaction with ozone. Although these products have not yet been characterized experimentally, the radical H(2)NO has been postulated, because it can regenerate NH(2) radicals through the reactions: H(2)NO + O(3) --> NH(2) + O(2) and H(2)NO + O(3) --> HNO + OH + O(2). With the purpose of providing a reasonable explanation from a theoretical point of view to the kinetic observed behaviour of the NH(2) + O(3) system, we have carried ab initio electronic structure calculations on both H(2)NO + O(3) possible reactions. The results obtained in this article, however, predict that of both reactions proposed, only the H(2)NO + O(3) --> NH(2) + O(2) reaction would regenerate indeed NH(2) radicals, explaining thus the deviation of the NH(2) pseudo-first-order decay observed experimentally.

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