Ultra-low temperature kinetics of neutral–neutral reactions: The reaction CN+O2 down to 26 K

Sims, Ian; Queffelec, J. L.; Defrance, A.; Rebrion-Rowe, C.; Travers, D.; Rowe, B. R.; Smith, Ian W. M.

doi:10.1063/1.463349

Cited by 86 publications

(52 citation statements)

References 13 publications

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“…In terms of overall reaction rate, only quite recently has the kinetic behavior of this reaction been accurately determined over a wide temperature range, from 26 K to 4000 K (4)(5)(6)(7). It was found that the thermal rate constant was relatively large and exhibited a pronounced negative temperature dependence, i.e., the rate constant decreased with increasing temperature.…”

Section: Introductionmentioning

confidence: 99%

Crossed-beam studies of radical reaction dynamics:

Macdonald¹,

Argonne²,

Sonnenfroh³

et al. 1994

Can. J. Chem.

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The title reaction has been studied in a crossed molecular beam apparatus. Both the product state distributions and the translational energy dependence of the reaction cross sections were measured under single collision conditions. Excellent agreement was found over a wide temperature range (26-3800 K) between rate constants deduced from the translational excitation function and recent thermal kinetic data. The rotational state distribution was found to be very cold compared to the reaction exothermicity, and could be described by a Boltzmann temperature of 1 10 K for all K-doublet levels. ' The vibronic state distribution was also found to be cold, with 70% of the products formed in the vibrational ground state. By comparing the molecular beam results for vibronic state distributions with those obtained from recent bulb experiments, it was conjectured that there appears to be a strong correlation between rotation in the reactants and bending excitation in the products.R. GLEN MACDONALD, KOPIN LIU, DAVID M. SONNENFROH et DI-JIA LIU. Can. J. Chem. 72,660 (1994). On a CtudiC la rCaction mentionnCe dans le titre i I'aide d'un appareil 6 faisceau molCculaire croisC. Utilisant des conditions de collision unique, on a CtudiC les distributions des Ctats des produits ainsi que la relation entre I'Cnergie de translation et les sections droites de la rCaction. Sur une large plage de tempkratures (26-3800 K), on a observC un excellent accord entre les constantes de vitesse obtenues i partir de la fonction d'excitation translationnelle et des donnCes rCcentes de cinCtique thermique. On a trouvC que la distribution de 1'Ctat rotationnel est trks froide si on la compare avec 1'exothermicitC de la rCaction et qu'on peut la dCcrire par une temperature de Boltzmann de 1 10 K pour tous les niveaux K-doublets. On a aussi trouvC que la distribution de I'Ctat vibronique est froide; en effet, 70% des produits se forment dans 1'Ctat vibrationnel fondamental. En comparant les rCsultats des faisceaux molCculaires pour les distributions de 1'Ctat vibronique avec ceux obtenus lors d'expkriences rCcentes avec des bulbes, on peut imaginer qu'il existe une forte corrilation entre la rotation des rCactifs et I'excitation de dCformation des produits.[Traduit par la rCdaction]

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Section: Introductionmentioning

confidence: 99%

Crossed-beam studies of radical reaction dynamics:

Macdonald¹,

Argonne²,

Sonnenfroh³

et al. 1994

Can. J. Chem.

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“…Practical difficulties to produce and measure radical concentrations made experimentalists to focus mainly on reactions which involve stable molecules. The development of new methods to investigate ultra low temperature kinetics, as the CRESU technique, 21 revealed however that reactions between neutral species could govern the dynamics at low-temperature regimes, for instance, in interstellar clouds. Recent examples of the possibilities of such approaches have been reported for the N+OH reaction.…”

Section: Introductionmentioning

confidence: 99%

An accurate study of the dynamics of the C+OH reaction on the second excited 14A″ potential energy surface

Zanchet

González‐Lezana

Roncero

et al. 2012

The Journal of Chemical Physics

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Dynamics study of the OH + NH3 hydrogen abstraction reaction using QCT calculations based on an analytical potential energy surface J. Chem. Phys. 138, 214306 (2013) The dynamics of the C( 3 P)+OH(X 2 ) → CO(a 3 )+H( 2 S) on its second excited potential energy surface, 1 4 A , have been investigated in detail by means of an accurate quantum mechanical (QM) time-dependent wave packet (TDWP) approach. Reaction probabilities for values of the total angular momentum J up to 50 are calculated and integral cross sections for a collision energy range which extends up to 0.1 eV are shown. The comparison with quasi-classical trajectory (QCT) and statistical methods reveals the important role played by the double well structure existing in the potential energy surface. The TDWP differential cross sections exhibit a forward-backward symmetry which could be interpreted as indicative of a complex-forming mechanism governing the dynamics of the process. The QM statistical method employed in this study, however, is not capable to reproduce the main features of the possible insertion nature in the reactive collision. The ability to stop individual trajectories selectively at specific locations inside the potential energy surface makes the QCT version of the statistical approach a better option to understand the overall dynamics of the process.

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“…Methods to experimentally extract information on these resonances are extremely limited. Thus far, low-energy collisions have only been studied in cryogenic cell environments (19 ), or in supersonic gas expansions that are specifically designed to maintain a thermal equilibrium at temperatures as low as 6 K (20 ). Recently, reports have appeared on the study of cold inelastic collisions between alkali atoms and dimers in an optically trapped gas (21,22 ).…”

mentioning

confidence: 99%

Near-Threshold Inelastic Collisions Using Molecular Beams with a Tunable Velocity

Gilijamse

Hoekstra

Meerakker

et al. 2006

Science

232

268

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Molecular scattering behavior has generally proven difficult to study at low collision energies. We formed a molecular beam of OH radicals with a narrow velocity distribution and a tunable absolute velocity by passing the beam through a Stark decelerator. The transition probabilities for inelastic scattering of the OH radicals with Xe atoms were measured as a function of the collision energy in range of 50 to 400 wavenumber, with an overall energy resolution of about 13 wavenumbers. The behavior of the cross sections for inelastic scattering near the energetic thresholds was accurately measured, and excellent agreement was obtained with cross-sections derived from coupled-channel calculations on ab initio computed potential energy surfaces.The study of collisions between gas-phase atoms and molecules is a well-established method of gathering detailed information about their individual structures and mutual interaction (1 ). The level of detail obtained by these studies depends on the quality of preparation of the collision partners before the collision (2-4 ) and on how accurately the products are analyzed afterward (5-7 ). In recent years, it has become increasingly possible to control the internal and external degrees of freedom of the scattering partners, allowing the potential energy surfaces that govern the molecular collisions to be probed in ever greater detail. The most detailed information is obtained when crossed molecular beams are used to produce intense jets of molecules with a well-defined velocity, confined to only a few internal quantum states. Further state selection can be achieved by optical preparation of a single quantum state or by purification of the beam with the use of electrostatic or magnetic multipole fields (2, 3 ). These methods allow the orientation of the molecules to be controlled before the collision (8, 9 ) and the orientation of the scattered products can be measured (10 ).One of the most important parameters describing a scattering event is the collision energy of the scatterers. However, control over the collision energy has been a difficult experimental task. Since the 1980's, ingenious crossed beam machines have been engineered to vary the crossing angle of the intersecting beams, allowing variation of the collision energy while maintaining particle densities high enough for scattering (11 ). It was thereby possible to measure threshold behavior of rotational energy transfer (12, 13 ), or to tune the collision energy over the reaction barrier for reactive scattering (14, 15 ). These methods led to considerable improvement in the control over collision energy at high energiesfor example to probe short-range interactions. However, a similar level of control over collisions at low energies, which are sensitive probes for long-range interactions, is generally lacking. The angle of the 1

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Ultra-low temperature kinetics of neutral–neutral reactions: The reaction CN+O2 down to 26 K

Abstract: Ultralow temperature kinetics of neutral-neutral reactions. The technique and results for the reactions CN+O2 down to 13 K and CN+NH3 down to 25 K

Cited by 86 publications

References 13 publications

Crossed-beam studies of radical reaction dynamics:

Crossed-beam studies of radical reaction dynamics:

An accurate study of the dynamics of the C+OH reaction on the second excited 14A″ potential energy surface

Near-Threshold Inelastic Collisions Using Molecular Beams with a Tunable Velocity

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