Cross Sections and Reaction Rates for Comparative Planetary Aeronomy

Huestis, D. L.; Bougher, S. W.; Fox, Jane L.; Galand, M.; Johnson, R. E.; Moses, J. I.; Pickering, J. C.

doi:10.1007/s11214-008-9383-7

Cited by 80 publications

(69 citation statements)

References 284 publications

(284 reference statements)

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“…It is well known that in hydrogen plasmas at room temperature the title reaction, and isotopologues, do not play a significant role in the proportion of the deuterated H + 3 . 8,9 However, at the lower temperatures of the interstellar medium, ≈10 K, these collisions are thought to be one of the most important ones in explaining the anomalous high proportion of deuterated triatomic hydrogen ions, 7 giving rise to the deuteration of other molecular species in space.…”

Section: Discussionmentioning

confidence: 99%

“…[1][2][3][4] Models to estimate the concentration of this cation, and its isotopomers, are used to follow the dynamics of ionospheres of outer planets as a function of solar fluence [5][6][7] and in isotopic exchange processes in low pressure plasmas of H 2 /D 2 mixtures. 8,9 H + 3 is formed in the H 2 + H + 2 → H + 3 + H reaction, and its deuterated variants via the subsequent HD + H + 3 → H 2 D + + H 2 proton-deuteron exchange reaction, and isotopic variants.…”

Section: Introductionmentioning

confidence: 99%

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Dynamically biased statistical model for the ortho/para conversion in the ${\rm H}_2 + {\rm H}_3^+$H2+H3+ → ${\rm H}_3^{+} +$H3++ H2 reaction

Gómez-Carrasco

González-Sánchez

Aguado

et al. 2012

The Journal of Chemical Physics

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In this work we present a dynamically biased statistical model to describe the evolution of the title reaction from statistical to a more direct mechanism, using quasi-classical trajectories (QCT). The method is based on the one previously proposed by Park and Light [J. Chem. Phys. 126, 044305 (2007)]. A recent global potential energy surface is used here to calculate the capture probabilities, instead of the long-range ion-induced dipole interactions. The dynamical constraints are introduced by considering a scrambling matrix which depends on energy and determine the probability of the identity/hop/exchange mechanisms. These probabilities are calculated using QCT. It is found that the high zero-point energy of the fragments is transferred to the rest of the degrees of freedom, what shortens the lifetime of H + 5 complexes and, as a consequence, the exchange mechanism is produced with lower proportion. The zero-point energy (ZPE) is not properly described in quasiclassical trajectory calculations and an approximation is done in which the initial ZPE of the reactants is reduced in QCT calculations to obtain a new ZPE-biased scrambling matrix. This reduction of the ZPE is explained by the need of correcting the pure classical level number of the H + 5 complex, as done in classical simulations of unimolecular processes and to get equivalent quantum and classical rate constants using Rice-Ramsperger-Kassel-Marcus theory. This matrix allows to obtain a ratio of hop/exchange mechanisms, α(T), in rather good agreement with recent experimental results by Crabtree et al. [J. Chem. Phys. 134, 194311 (2011)] at room temperature. At lower temperatures, however, the present simulations predict too high ratios because the biased scrambling matrix is not statistical enough. This demonstrates the importance of applying quantum methods to simulate this reaction at the low temperatures of astrophysical interest.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dynamically biased statistical model for the ortho/para conversion in the ${\rm H}_2 + {\rm H}_3^+$H2+H3+ → ${\rm H}_3^{+} +$H3++ H2 reaction

Gómez-Carrasco

González-Sánchez

Aguado

et al. 2012

The Journal of Chemical Physics

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“…In current non-LTE models, including the one applied in this study, it is usually assumed that k ν 2 −1,ν 2 = k 0,1 and k ν 2 ,ν 2 −1 = k 1,0 . It follows from Huestis et al (2008) that if the velocity distribution of O( 3 P) atoms is Maxwellian and their fine structure is thermalized then the laboratory measured k 0,1 and k 1,0 are linked by the detailed balance relation:…”

Section: Discussionmentioning

confidence: 99%

“…Generally, laboratory measurements provide low values of k VT centered around 1.3 × 10 −12 cm 3 s −1 . Huestis et al (2008), based on the analysis of experimental data and quantum-mechanical calculations, recommend using k VT = 1.5 × 10 −12 cm 3 s −1 . However, applying this value to the interpretation of I 15 µm measurements leads to overestimating the MLT temperatures.…”

Section: Introductionmentioning

confidence: 99%

CO<sub>2</sub>(ν<sub>2</sub>)-O quenching rate coefficient derived from coincidental SABER/TIMED and Fort Collins lidar observations of the mesosphere and lower thermosphere

et al. 2012

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Abstract. Among the processes governing the energy balance in the mesosphere and lower thermosphere (MLT), the quenching of CO 2 (ν 2 ) vibrational levels by collisions with O atoms plays an important role. However, there is a factor of 3-4 discrepancy between the laboratory measurements of the CO 2 -O quenching rate coefficient, k VT , and its value estimated from the atmospheric observations. In this study, we retrieve k VT in the altitude region 85-105 km from the coincident SABER/TIMED and Fort Collins sodium lidar observations by minimizing the difference between measured and simulated broadband limb 15 µm radiation. The averaged k VT value obtained in this work is 6.5 ± 1.5 × 10 −12 cm 3 s −1 that is close to other estimates of this coefficient from the atmospheric observations. However, the retrieved k VT also shows altitude dependence and varies from 5.5 ± 1.1 × 10 −12 cm 3 s −1 at 90 km to 7.9 ± 1.2 × 10 −12 cm 3 s −1 at 105 km. Obtained results demonstrate the deficiency in current non-LTE modeling of the atmospheric 15 µm radiation, based on the application of the CO 2 -O quenching and excitation rates, which are linked by the detailed balance relation. We discuss the possible model improvements, among them accounting for the interaction of the "non-thermal" oxygen atoms with CO 2 molecules.

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“…+ plays a central role in astrophysics as the most abundant ion in space and as the universal protonator [1][2][3][4], so that it is frequently used as a spectroscopic probe of the dynamics of ionospheres of outer planets [5,6]. It is then important to know in detail the rate constants of the collisions in which H 3 + participates.…”

Section: Hmentioning

confidence: 99%

Simulation of the infrared predissociation spectra of H5+

et al. 2012

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A quantum study of the bound states and infrared predissociation spectra of H 5 + is done using a recently proposed global and accurate potential-energy surface [Aguado et al., J. Chem. Phys. 133, 024306 (2010)]. The bound states are calculated for seven degrees of freedom using an iterative Lanczos method, yielding a dissociation energy in very good agreement with the available experimental data. The predissociation states are described by a wave-packet treatment considering a shared-proton model, in which the three-dimensional motion of the central atom is described using non-Jacobi bond coordinates. The justification of this model is that the change in the electric dipole moment is larger as a function of the motion of the central atom, responsible for the proton transfer in the H 3 + + H 2 → H 2 + H 3 + reaction. The electric dipole moment is calculated at the level of coupled-cluster theory with single and double excitations and fitted in nine dimensions to an analytical function. With it, the infrared predissociation spectrum is simulated, yielding a reasonable agreement with recent measurements.

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Cross Sections and Reaction Rates for Comparative Planetary Aeronomy

Cited by 80 publications

References 284 publications

Dynamically biased statistical model for the ortho/para conversion in the ${\rm H}_2 + {\rm H}_3^+$H2+H3+ → ${\rm H}_3^{+} +$H3++ H2 reaction

Dynamically biased statistical model for the ortho/para conversion in the ${\rm H}_2 + {\rm H}_3^+$H2+H3+ → ${\rm H}_3^{+} +$H3++ H2 reaction

CO<sub>2</sub>(ν<sub>2</sub>)-O quenching rate coefficient derived from coincidental SABER/TIMED and Fort Collins lidar observations of the mesosphere and lower thermosphere

Simulation of the infrared predissociation spectra of H5+

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Cross Sections and Reaction Rates for Comparative Planetary Aeronomy

Cited by 80 publications

References 284 publications

Dynamically biased statistical model for the ortho/para conversion in the ${\rm H}_2 + {\rm H}_3^+$H2+H3+ → ${\rm H}_3^{+} +$H3++ H2 reaction

Dynamically biased statistical model for the ortho/para conversion in the ${\rm H}_2 + {\rm H}_3^+$H2+H3+ → ${\rm H}_3^{+} +$H3++ H2 reaction

CO&lt;sub&gt;2&lt;/sub&gt;(ν&lt;sub&gt;2&lt;/sub&gt;)-O quenching rate coefficient derived from coincidental SABER/TIMED and Fort Collins lidar observations of the mesosphere and lower thermosphere

Simulation of the infrared predissociation spectra of H5+

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CO<sub>2</sub>(ν<sub>2</sub>)-O quenching rate coefficient derived from coincidental SABER/TIMED and Fort Collins lidar observations of the mesosphere and lower thermosphere