Comparison of the cross-sections and thermal rate constants for the reactions of C(3PJ) atoms with O2 and NO

Geppert, Wolf D.; Reignier, D.; Stoecklin, Thierry; Naulin, Christian; Costes, Michel; Chastaing, Delphine; Picard, S.; Sims, Ian; Smith, Ian W. M.

doi:10.1039/b002583f

Cited by 54 publications

(66 citation statements)

References 34 publications

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“…with the reaction constants293031 of k C2 = 2.25 × 10 −11 ( T/T r ) cm 3 molecules −1 s −1 and k C = 5.1 × 10 −11 ( T r /T ) 0.3 cm 3 molecules −1 s −1 . Again, these reactions in the quasi-equilibrium state for the number of carbon atoms lead to…”

Section: Resultsmentioning

confidence: 99%

Disintegration of Carbon Dioxide Molecules in a Microwave Plasma Torch

Kwak

Uhm

Hong

et al. 2015

Sci Rep

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A pure carbon dioxide torch is generated by making use of 2.45 GHz microwave. Carbon dioxide gas becomes the working gas and produces a stable carbon dioxide torch. The torch volume is almost linearly proportional to the microwave power. Temperature of the torch flame is measured by making use of optical spectroscopy and thermocouple. Two distinctive regions are exhibited, a bright, whitish region of high-temperature zone and a bluish, dimmer region of relatively low-temperature zone. Study of carbon dioxide disintegration and gas temperature effects on the molecular fraction characteristics in the carbon dioxide plasma of a microwave plasma torch under atmospheric pressure is carried out. An analytical investigation of carbon dioxide disintegration indicates that substantial fraction of carbon dioxide molecules disintegrate and form other compounds in the torch. For example, the normalized particle densities at center of plasma are given by nCO2/nN = 6.12 × 10−3, nCO/nN = 0.13, nC/nN = 0.24, nO/nN = 0.61, nC2/nN = 8.32 × 10−7, nO2/nN = 5.39 × 10−5, where nCO2, nCO, nC, nO, nC2, and nO2 are carbon dioxide, carbon monoxide, carbon and oxygen atom, carbon and oxygen molecule densities, respectively. nN is the neutral particle density. Emission profiles of the oxygen and carbon atom radicals and the carbon monoxide molecules confirm the theoretical predictions of carbon dioxide disintegration in the torch.

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Section: Resultsmentioning

confidence: 99%

Disintegration of Carbon Dioxide Molecules in a Microwave Plasma Torch

Kwak

Uhm

Hong

et al. 2015

Sci Rep

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“…9). These latter two reactions have wellconstrained rate coefficients (Geppert et al 2000;Miller et al 2005). Gas-phase O 2 is able to persist in the disk atmosphere for the same reasons as gas-phase H 2 O: the gas temperature is sufficiently high to activate the required neutral-neutral chemical reactions.…”

Section: On the Abundance Of O 2 In Protoplanetary Disksmentioning

confidence: 99%

The molecular composition of the planet-forming regions of protoplanetary disks across the luminosity regime

Walsh

Nomura

Dishoeck

2015

A&A

188

329

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Context. Near-to mid-infrared observations of molecular emission from protoplanetary disks show that the inner regions are rich in small organic volatiles (e.g., C 2 H 2 and HCN). Trends in the data suggest that disks around cooler stars (T eff ≈ 3000 K) are potentially (i) more carbon-rich; and (ii) more molecule-rich than their hotter counterparts (T eff > ∼ 4000 K). Aims. We explore the chemical composition of the planet-forming region (<10 AU) of protoplanetary disks around stars over a range of spectral types (from M dwarf to Herbig Ae) and compare with the observed trends. Methods. Self-consistent models of the physical structure of a protoplanetary disk around stars of different spectral types are coupled with a comprehensive gas-grain chemical network to map the molecular abundances in the planet-forming zone. The effects of (i) N 2 self shielding; (ii) X-ray-induced chemistry; and (iii) initial abundances, are investigated. The chemical composition in the "observable" atmosphere is compared with that in the disk midplane where the bulk of the planet-building reservoir resides. Results. M dwarf disk atmospheres are relatively more molecule rich than those for T Tauri or Herbig Ae disks. The weak far-UV flux helps retain this complexity which is enhanced by X-ray-induced ion-molecule chemistry. N 2 self shielding has only a small effect in the disk molecular layer and does not explain the higher C 2 H 2 /HCN ratios observed towards cooler stars. The models underproduce the OH/H 2 O column density ratios constrained in Herbig Ae disks, despite reproducing (within an order of magnitude) the absolute value for OH: the inclusion of self shielding for H 2 O photodissociation only increases this discrepancy. One possible explanation is the adopted disk structure. Alternatively, the "hot" H 2 O (T > ∼ 300 K) chemistry may be more complex than assumed. The results for the atmosphere are independent of the assumed initial abundances; however, the composition of the disk midplane is sensitive to the initial main elemental reservoirs. The models show that the gas in the inner disk is generally more carbon rich than the midplane ices. This effect is most significant for disks around cooler stars. Furthermore, the atmospheric C/O ratio appears larger than it actually is when calculated using observable tracers only. This is because gas-phase O 2 is predicted to be a significant reservoir of atmospheric oxygen.Conclusions. The models suggest that the gas in the inner regions of disks around cooler stars is more carbon rich; however, calculations of the molecular emission are necessary to definitively confirm whether the chemical trends reproduce the observed trends.

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“…This has been found to be the case, within experimental error, for a number of reactions, including for example the reactions of C( 3 P) atoms with O 2 and NO. 31 When similar agreement was not found for the reaction of C( 3 P) atoms with C 2 H 2 , 32 the discrepancy was attributed to a temperature-dependent branching to a spin-forbidden product channel (C 3 + H 2 in this case).…”

Section: Neutral-neutral Reactionsmentioning

confidence: 56%