Low-temperature kinetics of reactions between neutral free radicals. Rate constants for the reactions of OH radicals with N atoms (103 ⩽T/K ⩽ 294) and with O atoms (158 ⩽T/K ⩽ 294)

Smith, Ian W. M.; Stewart, David W.

doi:10.1039/ft9949003221

Cited by 77 publications

(88 citation statements)

References 54 publications

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“…From the dynamical point of view, such systems with two heavy atoms usually involve potential energy surfaces which present deep potential wells and many channels have to be considered to get converged results. The title reaction has been the subject of many theoretical [11][12][13][14][15] and experimental [16][17][18][19] works. Experimentalists, in general, have focused on the determination of thermal rate constants.…”

Section: Introductionmentioning

confidence: 99%

“…Experimentalists, in general, have focused on the determination of thermal rate constants. Smith and co-workers 18,19 have obtained experimental rate constants down to 103 K using discharge-flow and flash photolysis techniques. They found that the rate constant increases as the temperature decreases, and the measured thermal rate constants were found to present a nonlinear Arrhenius behavior over the temperature range studied.…”

Section: Introductionmentioning

confidence: 99%

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Accurate time dependent wave packet calculations for the N + OH reaction

Bulut

Roncero

Jorfi

et al. 2011

The Journal of Chemical Physics

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We present accurate quantum calculations of state-to-state cross sections for the N + OH → NO + H reaction performed on the ground 3 A global adiabatic potential energy surface of Guadagnini et al. [J. Chem. Phys. 102, 774 (1995)]. The OH reagent is initially considered in the rovibrational state v = 0, j = 0 and wave packet calculations have been performed for selected total angular momentum, J = 0, 10, 20, 30, 40,...,120. Converged integral state-to-state cross sections are obtained up to a collision energy of 0.5 eV, considering a maximum number of eight helicity components, = 0,...,7. Reaction probabilities for J = 0 obtained as a function of collision energy, using the wave packet method, are compared with the recently published time-independent quantum mechanical one. Total reaction cross sections, state-specific rate constants, opacity functions, and product state-resolved integral cross-sections have been obtained by means of the wave packet method for several collision energies and compared with recent quasi-classical trajectory results obtained with the same potential energy surface. The rate constant for OH(v = 0, j = 0) is in good agreement with the previous theoretical values, but in disagreement with the experimental data, except at 300 K.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Accurate time dependent wave packet calculations for the N + OH reaction

Bulut

Roncero

Jorfi

et al. 2011

The Journal of Chemical Physics

View full text Add to dashboard Cite

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“…This assumption allows one to calculate hypothetical rate coefficients, k'(T), for only those collisions occurring on the ground electronic surface. They have been shown (Smith & Stewart 1994) to correlate quite well with the expression: k'(T) = k' 29S (T/298) n and it has been suggested that the best estimate of rate coefficients for such reactions below 100 Κ can be made by extrapolating the values of k'(T) to these temperatures and then correcting by the appropriate values of F e iec-F°r reactions (5) …”

Section: Reactions Between Atomic and Diatomic Radicalsmentioning

confidence: 81%

“…species, other than O2 and NO, with unpaired electrons). Such measurements have been made in cryogenically cooled cells for the reactions between Ν and Ο atoms and OH and CH (Smith & Stewart 1994, Brownsword et al 1996c. A modification of the PLP-LIF technique was employed in which atomic radicals were created by dissociating N2 in a microwave discharge.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Fig. 3 shows the rate coefficients obtained (Smith & Stewart 1994) for the reactions Such systems are characterised by the existence of multiple potential energy surfaces arising from the degenerate and near-degenerate fine structure states in the radical reagents (Smith 1991). As a result, part of the temperature dependence of the rate coefficients shown in Fig.…”

Section: Reactions Between Atomic and Diatomic Radicalsmentioning

confidence: 99%

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Reactions between neutral species at low temperatures: Laboratory results and astrophysical modelling

Smith

1997

Symp. - Int. Astron. Union

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Abstract.Over the past few years, rate coefficients (k) have been measured for neutral-neutral reactions at low (down to 80 K) and ultra-low (down to 13 K) temperatures (T). The experimental methods and the results which have been obtained are reviewed. A surprisingly large number of reactions become faster at lower temperatures and have rate coefficients close to the collisional value below ca. 50 K. The factors which influence the form of k(T) are briefly discussed and proposals are made as to how rate coefficients might be estimated for use in astrochemical models.

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Perchlorate formation on Mars through surface radiolysis‐initiated atmospheric chemistry: A potential mechanism

et al. 2016

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Recent observations of the Martian surface by the Phoenix lander and the Sample Analysis at Mars indicate the presence of perchlorate (ClO 4 – ). The abundance and isotopic composition of these perchlorates suggest that the mechanisms responsible for their formation in the Martian environment may be unique in our solar system. With this in mind, we propose a potential mechanism for the production of Martian perchlorate: the radiolysis of the Martian surface by galactic cosmic rays, followed by the sublimation of chlorine oxides into the atmosphere and their subsequent synthesis to form perchloric acid (HClO 4 ) in the atmosphere, and the surface deposition and subsequent mineralization of HClO 4 in the regolith to form surface perchlorates. To evaluate the viability of this mechanism, we employ a one‐dimensional chemical model, examining chlorine chemistry in the context of Martian atmospheric chemistry. Considering the chlorine oxide, OClO, we find that an OClO flux as low as 3.2 × 10 7 molecules cm –2 s –1 sublimated into the atmosphere from the surface could produce sufficient HClO 4 to explain the perchlorate concentration on Mars, assuming an accumulation depth of 30 cm and integrated over the Amazonian period. Radiolysis provides an efficient pathway for the oxidation of chlorine, bypassing the efficient Cl/HCl recycling mechanism that characterizes HClO 4 formation mechanisms proposed for the Earth but not Mars.

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Low-temperature kinetics of reactions between neutral free radicals. Rate constants for the reactions of OH radicals with N atoms (103 ⩽T/K ⩽ 294) and with O atoms (158 ⩽T/K ⩽ 294)

Cited by 77 publications

References 54 publications

Accurate time dependent wave packet calculations for the N + OH reaction

Accurate time dependent wave packet calculations for the N + OH reaction

Reactions between neutral species at low temperatures: Laboratory results and astrophysical modelling

Perchlorate formation on Mars through surface radiolysis‐initiated atmospheric chemistry: A potential mechanism

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