Dissociative electron attachment to methylacetylene and dimethylacetylene: Symmetry versus proximity

Janečková, Radmila; May, Olivier; Fedor, Juraj

doi:10.1103/physreva.86.052702

Cited by 10 publications

(6 citation statements)

References 42 publications

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“…Further, threshold energies were estimated for the dissociative electron attachment (DEA) reactions at the same level of theory. The reliability of the approach is well-known from previous studies (e.g., refs and ). Individual threshold energy calculations were based on the formula where E M a – and E M b are the energies of the breakup products in the DEA process, for a newly formed stable negative ion and its neutral part, respectively.…”

Section: Theoretical Methodsmentioning

confidence: 69%

Carboxylation Enhances Fragmentation of Furan upon Resonant Electron Attachment

2020

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We report a dissociative electron attachment study to 2-furoic acid (C 5 H 4 O 3 ) isolated in a gas phase, which is a model molecule consisting of a carboxylic group and a furan ring. Dissociation of furan by low energy electrons is accessible only via electronic excited Feshbach resonances at energies of incident electrons above 5 eV. On the other hand, carboxylic acids are well-known to dissociate via attachment of electrons at subexcitation energies. Here we elucidate how the electron and proton transfer reactions induced by carboxylation influence stability of the furan ring. Overlap of the furan and carboxyl π orbitals results in transformation of the nondissociative π 2 resonance of the furan ring to a dissociative resonance. The interpretation of hydrogen transfer reactions is supported by experimental studies of 3-methyl-2-furoic and 5-methyl-2-furoic acids (C 6 H 6 O 3 ) and density functional theory (DFT) calculations.

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Section: Theoretical Methodsmentioning

confidence: 69%

Carboxylation Enhances Fragmentation of Furan upon Resonant Electron Attachment

2020

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“…The theoretical results were validated by a favorable comparison with experimental cross sections, both in terms of the absolute values [7] and the isotope effect [8]. The symmetry lowering pathway prevails also in propyne CH 3 C ---C-H where the acetylenic C-H bond was found to break, although the methyl group CH 2 -H bond could break without symmetry lowering [9]. The symmetry-lowering mechanism is common among compounds with bonds; two other important examples are vinyl chloride and chlorobenzene [10,11].…”

mentioning

confidence: 75%

“…This value is consistent with that used to normalize our previous work, for example Refs. [8,9]. The error of the absolute measurement (2 standard deviations) is taken as AE20% and it includes the AE15% error of the reference O À from CO 2 value.…”

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confidence: 99%

Experimental Evidence on the Mechanism of Dissociative Electron Attachment to Formic Acid

et al. 2013

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Two mechanisms for dissociative electron attachment in HCOOH, the formation of HCOO À þ H, were proposed in the literature: (i) via a direct electron attachment into a Ã resonance, augmented by dipole binding of the incident electron [G. A. Gallup et al., Phys. Rev. A 79, 042701 (2009)], and (ii) with the 1.8 eV Ã resonance as a doorway state, linked to the products by symmetry lowering-distortion of the temporary anion, primarily the C-H bond, from the planar symmetry [T. N. Rescigno et al., Phys. Rev. Lett. 96, 213201 (2006)]. The later mechanism implies a reduction of the cross section upon deuteration of the hydrogen bonded to the C atom, whereas the former mechanism would leave the cross section unaffected. Our experimental absolute cross sections for the four isotopomers of formic acid show that deuteration on the C atom reduces the cross section value only marginally (by 12%) compared to deuteration on the O atom (reduction by a factor of 16), and thus favor mechanism (i).

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“…Also, the cross-section is about one order of magnitude lower than the value previously estimated (9.4 × 10 −18 versus 2.0 × 10 −16 cm 2 ). Finally, dissociative electron attachment to H 2 (Krishnakumar et al, 2011), CH 3 CCH (Janečková et al, 2012), NH 3 (Rawat et al, 2008), HNC (Chourou and Orel, 2009) and C 4 N 2 (Graupner et al, 2008) are now included, as some data became available since our previous publication.…”

Section: Reaction Class Chemical Equation Neutral Speciesmentioning

confidence: 99%

Simulating the density of organic species in the atmosphere of Titan with a coupled ion-neutral photochemical model

Vuitton

Yelle

Klippenstein

et al. 2019

Icarus

165

362

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We present a one-dimensional coupled ion-neutral photochemical kinetics and diffusion model to study the atmospheric composition of Titan in light of new theoretical kinetics calculations and scientific findings from the Cassini-Huygens mission. The model extends from the surface to the exobase. The atmospheric background, boundary conditions, vertical transport and aerosol opacity are all constrained by the Cassini-Huygens observations. The chemical network includes reactions between hydrocarbons, nitrogen and oxygen bearing species. It takes into account neutrals and both positive and negative ions with masses extending up to about 100 u. We incorporate high-resolution isotopic photoabsorption and photodissociation cross sections for N 2 as well as new photodissociation branching ratios for CH 4 and C 2 H 2 . Ab initio transition state theory calculations are performed in order to estimate the rate coefficients and products for critical reactions.Main reactions of production and loss for neutrals and ions are quantitatively assessed and thoroughly discussed. The vertical distributions of neutrals and ions predicted by the model generally reproduce observational data, suggesting that for the small species most chemical processes in Titan's atmosphere and ionosphere are adequately described and understood; some differences are highlighted. Notable remaining issues include (i) the total positive ion density (essentially HCNH + ) in the upper ionosphere, (ii) the low mass negative ion densities (CN -, C 3 N -/C 4 H -) in the upper atmosphere, and (iii) the minor oxygen-bearing species (CO 2 , H 2 O) density in the stratosphere. Pathways towards complex molecules and the impact of aerosols (UV shielding, atomic and molecular hydrogen budget, nitriles heterogeneous chemistry and condensation) are evaluated in the model, along with lifetimes and solar cycle variations.

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Dissociative electron attachment to methylacetylene and dimethylacetylene: Symmetry versus proximity

Cited by 10 publications

References 42 publications

Carboxylation Enhances Fragmentation of Furan upon Resonant Electron Attachment

Carboxylation Enhances Fragmentation of Furan upon Resonant Electron Attachment

Experimental Evidence on the Mechanism of Dissociative Electron Attachment to Formic Acid

Simulating the density of organic species in the atmosphere of Titan with a coupled ion-neutral photochemical model

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