Kinetic Investigation of the Reactions of Mg(1S), Ca(1S), and Sr(1S) Atoms with NO2 over the Temperature Ranges 303−836, 303−916, and 303−986 K, Respectively

Vinckier, Chris; Helaers, Joëlle; Christiaens, P; Remeysen, Jan

doi:10.1021/jp9920500

Cited by 9 publications

(9 citation statements)

References 23 publications

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“…MgO was produced by the addition of O 3 downstream of the Mg oven Mg + normalO 3 → MgO + normalO 2 goodbreak0em2em⁣ normalΔ H 0 normalK = prefix− 147 .25em kJ .25em mol prefix− 1 In previous work on CaO and FeO kinetics, we used the reactions of Ca and Fe with NO 2 to produce CaO and FeO, respectively. , However, at room temperature, Mg is unreactive toward NO 2 ; hence, it is not a suitable oxidant in the flow tube . The problem with using O 3 as the oxidant is that MgO then reacts to produce MgO 2 MgO + normalO 3 → MgO 2 + normalO 2 goodbreak0em2em⁣ normalΔ H 0 normalK = prefix− 231 .25em kJ .25em mol prefix− 1 However, as k 6 and k 7 have been measured previously, it was possible to retrieve k 1 and k 2 simultaneously using a two-dimensional (2D) χ 2 minimization model .…”

Section: Resultsmentioning

confidence: 99%

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A New Model for Magnesium Chemistry in the Upper Atmosphere

Plane

Whalley

2012

J. Phys. Chem. A

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This paper describes the kinetic study of a number of gas-phase reactions involving neutral Mg-containing species, which are important for the chemistry of meteor-ablated magnesium in the upper mesosphere/lower thermosphere region. The study is motivated by the very recent observation of the global atomic Mg layer around 90 km, using satellite-born UV-visible spectroscopy. In the laboratory, Mg atoms were produced thermally in the upstream section of a fast flow tube and then converted to the molecular species MgO, MgO(2), OMgO(2), and MgCO(3) by the addition of appropriate reagents. Atomic O was added further downstream, and Mg was detected at the downstream end of the flow tube by laser-induced fluorescence. The following rate coefficients were determined at 300 K: k(MgO + O → Mg + O(2)) = (6.2 ± 1.1) × 10(-10); k(MgO(2) + O → MgO + O(2)) = (8.4 ± 2.8) × 10(-11); k(MgCO(3) + O → MgO(2) + CO(2)) ≥ 4.9 × 10(-12); and k(MgO + CO → Mg + CO(2)) = (1.1 ± 0.3) × 10(-11) cm(3) molecule(-1) s(-1). Electronic structure calculations of the relevant potential energy surfaces combined with RRKM theory were performed to interpret the experimental results and also to explore the likely reaction pathways that convert MgCO(3) and OMgO(2) into long-lived reservoir species such as Mg(OH)(2). Although no reaction was observed in the laboratory between OMgO(2) and O, this is most likely due to the rapid recombination of O(2) with the product MgO(2) to form the relatively stable O(2)MgO(2). Indeed, one significant finding is the role of O(2) in the mesosphere, where it initiates holding cycles by recombining with radical species such as MgO(2) and MgOH. A new atmospheric model was then constructed which combines these results together with recent work on magnesium ion-molecule chemistry. The model is able to reproduce satisfactorily some of the key features of the Mg and Mg(+) layers, including the heights of the layers, the seasonal variations of their column abundances, and the unusually large Mg(+)/Mg ratio.

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Section: Resultsmentioning

confidence: 99%

“…15,16 However, at room temperature, Mg is unreactive toward NO 2 ; hence, it is not a suitable oxidant in the flow tube. 22 The problem with using O 3 as the oxidant is that MgO then reacts to produce MgO 2…”

Section: ■ Resultsmentioning

confidence: 99%

A New Model for Magnesium Chemistry in the Upper Atmosphere

Plane

Whalley

2012

J. Phys. Chem. A

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“…The reaction between Ca and NO 2 has been studied previously by Vinckier et al in the temperature range 303-916 K, 24 Although both surfaces have stable adducts with relatively deep minima,…”

Section: Discussionmentioning

confidence: 98%

A kinetic study of reactions of calcium-containing molecules with O and H atoms: implications for calcium chemistry in the upper atmosphere

Plane

2010

Phys. Chem. Chem. Phys.

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This paper describes the kinetic study of a number of gas-phase reactions involving neutral Ca-containing species, many of which are important for describing the chemistry of meteor-ablated calcium in the Earth's upper atmosphere. Ca atoms were produced thermally in the upstream section of a fast flow tube, and then converted to the molecular species CaO, CaO(2), CaO(3), CaCO(3) or Ca(OH)(2) by the addition of appropriate reagents. Atomic O or H was added further downstream, and both Ca and CaO were detected at the downstream end of the flow tube by laser-induced fluorescence. The following rate coefficients were determined: k(CaO + O --> Ca + O(2)) = (3.1) x 10(-10) at 300 K and (1.3) x 10(-10) at 203 K; k(CaO(2) + O --> CaO + O(2)) = (2.2) x 10(-11) at 300 K and (1.6) x 10(-11) at 203 K; k(CaO(2) + H --> products, 298 K) = (1.2 +/- 0.6) x 10(-11); k(CaCO(3) + O --> CaO(2) + CO(2), 300 K) < or = 1.0 x 10(-12); k(CaCO(3) + H--> CaOH + CO(2), 298 K) > or = 2.8 x 10(-12) and < or = 3.6 x 10(-11); k(CaO(3) + H--> CaOH + O(2), 298 K) > or = 1.7 x 10(-11); k(Ca(OH)(2) + H --> CaOH + H(2)O, 298 K) > or = 1.1 x 10(-11); k(CaOH + H --> Ca + H(2)O, 298 K) > or = 1.1x 10(-11) cm(3) molecule(-1) s(-1). The kinetics of the reactions of Ca and CaO with NO(2) and N(2)O were also studied, yielding k(Ca + NO(2) --> CaO + NO) = (2.6 +/- 0.3) x 10(-10) at 300 K and (2.0 +/- 0.3) x 10(-10) at 203 K; k(CaO + NO(2) --> CaO(2) + NO) = (8.1 +/- 2.0) x 10(-10) at 300 K and (2.9 +/- 1.0) x 10(-10) at 202 K; k(CaO + N(2)O --> CaO(2) + N(2)) = (4.2 +/- 1.7) x 10(-11) at 300 K and (2.2 +/- 1.2) x 10(-12) at 206 K; k(CaO + H(2) --> Ca + H(2)O, 300 K) = (3.4 +/- 1.3) x 10(-10) cm(3) molecule(-1) s(-1). Electronic structure calculations of the relevant potential energy surfaces were performed to interpret the experimental results, and the atmospheric implications of these measurements are then discussed.

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“…k etm = 1.4 × 10 -10 cm 3 molecule -1 s -1 ; thus, the simple electron transfer mechanism is not an adequate explanation. Another model that has been used successfully for metal + small oxidant systems is based on attractive dispersive forces that give interaction cross sections that are greater than σ etm . , The rate constant, termed k C 6 here, is given by where ε is the attractive potential between the colliders, k is the Boltzmann constant, T is the absolute temperature, v is defined as above, and Γ is the gamma function. ε is taken as the C 6 coefficient for the attractive term in the Lennard-Jones 6-12 potential.…”

Section: Discussionmentioning

confidence: 99%

Depletion Kinetics of Chromium Atoms by Sulfur Dioxide

McClean

2000

J. Phys. Chem. A

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The gas-phase depletion kinetics of Cr(a 7 S 3 , a 5 S 2 , a 5 D J ) in the presence of SO 2 are reported. Chromium atoms were produced by the 248 nm photodissociation of chromium carbonyl and were detected by laser-induced fluorescence. The ground state of Cr, a 7 S 3 , was found to react rapidly via a termolecular mechanism with SO 2 . At 297 K, the limiting low-pressure third-order rate constant is k o ) (2.68 ( 0.41) × 10 -28 cm 6 molecule -2 s -1 , and the limiting high-pressure second-order rate constant is k ∞ ) (2.73 ( 0.38) × 10 -10 cm 3 molecule -1 s -1 ; the uncertainties represent (1σ in precision. k o was found to decrease with increasing temperature. The binding energy of CrSO 2 is estimated at 53 kcal mol -1 from combining the kinetic results with unimolecular rate theory and density functional theory. Cr(a 5 S 2 ) depleted with a rate constant of k ) 6.32 × 10 -10 cm 3 molecule -1 s -1 , and the a 5 D J spin/orbit states depleted at the collision rate of 2.97 × 10 -10 cm 3 molecule -1 s -1 ; overall uncertainties are estimated at e35%. Both chemical and physical quenching are likely for the excited states. The present work completes a study on the depletion kinetics of group 6 transition metal atoms by SO 2 . Results are interpreted in terms of long-range attractive forces between Cr and SO 2 and the orbital occupancies of the Cr atomic states.

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Kinetic Investigation of the Reactions of Mg(¹S), Ca(¹S), and Sr(¹S) Atoms with NO₂ over the Temperature Ranges 303−836, 303−916, and 303−986 K, Respectively

Cited by 9 publications

References 23 publications

A New Model for Magnesium Chemistry in the Upper Atmosphere

A New Model for Magnesium Chemistry in the Upper Atmosphere

A kinetic study of reactions of calcium-containing molecules with O and H atoms: implications for calcium chemistry in the upper atmosphere

Depletion Kinetics of Chromium Atoms by Sulfur Dioxide

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