Dissociative Charge Transfer of Argon Ions with Methane Molecules from Ultralow to Superthermal Collision Energies

Tosi, Paolo; Cappelletti, David; Dmitriev, O.; Giordani, Sara; Bassi, Davide; Latimer, Darin R.; Smith, Mark A.

doi:10.1021/j100042a031

Cited by 13 publications

(10 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The dissociative and non-dissociative charge transfer of rare gas cations on methane is well-documented and efficient near resonant charge transfers are observed. [66][67][68][69][70][71][72][73] For charge transfer processes involving reactions of atomic A + ions with molecule targets such as methane, two criteria are usually important for a good coupling between charge transfer states, the good overlap between CH 4 (v=0) and CH reaction at E CM = 0.2 eV, i.e. with the same total initial energy (about 5 eV), but with two very opposite repartitions between O + internal energy and collision energy, are very different (see last point in Figure 5 and first point in Figure 7).…”

Section: Discussionmentioning

confidence: 99%

Reactions of State-Selected Atomic Oxygen Ions O⁺(⁴S, ²D, ²P) with Methane

et al. 2015

View full text Add to dashboard Cite

An experimental study has been carried out on the reactions of state selected O(+)((4)S, (2)D, (2)P) ions with methane with the aims of characterizing the effects of both the parent ion internal energy and collision energy on the reaction dynamics and determining the fate of oxygen species in complex media, in particular the Titan ionosphere. Absolute cross sections and product velocity distributions have been determined for the reactions of (16)O(+) or (18)O(+) ions with CH4 or CD4 from thermal to 5 eV collision energies by using the guided ion beam (GIB) technique. Dissociative photoionization of O2 with vacuum ultraviolet (VUV) synchrotron radiation delivered by the DESIRS beamline at the SOLEIL storage ring and the threshold photoion photoelectron coincidence (TPEPICO) technique are used for the preparation of purely state-selected O(+)((4)S, (2)D, (2)P) ions. A complete inversion of the product branching ratio between CH4(+) and CH3(+) ions in favor of the latter is observed for excitation of O(+) ions from the (4)S ground state to either the (2)D or the (2)P metastable state. CH4(+) and CH3(+) ions, which are by far the major products for the reaction of ground state and excited states, are strongly backward scattered in the center of mass frame relative to O(+) parent ions. For the reaction of O(+)((4)S), CH3(+) production also rises with increasing collision energy but with much less efficiency than with O(+) excitation. We found that a mechanism of dissociative charge transfer, mediated by an initial charge transfer step, can account very well for all the observations, indicating that CH3(+) production is associated with the formation of H and O atoms (CH3(+) + H + O) rather than with OH formation by an hydride transfer process (CH3(+) + OH). Therefore, as the CH4(+) production by charge transfer is also associated with O atoms, the fate of oxygen species in these reactions is essentially the O production, except for the reaction of O(+)((4)S), which also produces appreciable amounts of H2O(+) ions but only at very low collision energy. The production of O atoms and the nature of the states in which they are formed are discussed for the reactions of O(+) ions with CH4 and N2.

show abstract

Section: Discussionmentioning

confidence: 99%

Reactions of State-Selected Atomic Oxygen Ions O⁺(⁴S, ²D, ²P) with Methane

et al. 2015

View full text Add to dashboard Cite

show abstract

“…These branching fractions are largely independent of collision energy up to 4 eV and temperatures from 300 to 700 K, suggesting that the collision energy is not effectively coupled to the internal modes of the CH 4 + product, while the thermal excitation of CH 4 at 700 K is small relative to the exothermicity of 5. 33,34 As there are no energetically accessible excited electronic states of Ar, the remainder of the reaction energy must be distributed into kinetic energy of the products. Comparison with threshold photoelectron−photoion coincidence spectroscopy measurements suggest that on average 87% of the total exothermicity of the reaction is funneled into internal excitation of the CH 4 + product.…”

Section: ■ Discussionmentioning

confidence: 99%

Kinetics and Product Branching Fractions of Reactions between a Cation and a Radical: Ar⁺ + CH₃ and O₂⁺ + CH₃

et al. 2015

View full text Add to dashboard Cite

A novel technique is described for the measurement of rate constants and product branching fractions of thermal reactions between cation and radical species. The technique is a variant of the variable electron and neutral density attachment mass spectrometry (VENDAMS) method, employing a flowing afterglow-Langmuir probe apparatus. A radical species is produced in situ via dissociative electron attachment to a neutral precursor; this allows for a quantitative derivation of the radical concentration and, as a result, a quantitative determination of rate constants. The technique is applied to the reactions of Ar(+) and O2(+) with CH3 at 300 K. The Ar(+) + CH3 reaction proceeds near the collisional rate constant of 1.1 × 10(-9) cm(3) s(-1) and has three product channels: → CH3(+) + Ar (k = 5 ± 2 × 10(-10) cm(3) s(-1)), → CH2(+) + H + Ar (k = 7 ± 2 × 10(-10) cm(3) s(-1)), → CH(+) + H2 + Ar (k = 5 ± 3 × 10(-11) cm(3) s(-1)). The O2(+) + CH3 reaction is also efficient, with direct charge transfer yielding CH3(+) as the primary product channel. Several results needed to support these measurements are reported, including the kinetics of Ar(+) and O2(+) with CH3I, electron attachment to CH3I, and mutual neutralization of CH3(+) and CH2(+) with I(-).

show abstract

“…Energy-resolved reaction rates and branching ratios for the reaction Ar + + CH 4 → products were taken from (8), which has rate constants for the energy range from 5 • 10 −4 to 4 eV. The total rate constant given in the energy range under consideration is 1.41…”

Section: Inclusion Of Argon Plasmas In Eromentioning

confidence: 99%

Carbon transport and escape fraction in a high density plasma beam

Swaaij¹,

Bystrov²,

Borodin³

et al. 2013

Journal of Nuclear Materials

View full text Add to dashboard Cite

Hydrocarbon injection experiments on molybdenum targets facing high-density plasmas in Pilot-PSI were simulated with the 3D Monte Carlo impurity transport and PSI code ERO. Impurity transport and calculation of redeposition profiles were decoupled by calculating carbon redistribution matrices with ERO. Redeposition was found to be strongly dependent on the electron density. The calculated average number of recycling events of hydrocarbon molecules on the surface went up from from 1.5 for n e = 5 • 10 19 m −3 to 19.2 for n e = 4 • 10 20 m −3 ; at the latter density, only 2.4% of the hydrocarbon molecules escapes the simulated plasma beam without returning to the target at least once. Agreement with experimental deposition profiles in argon was fair. The results in hydrogen point towards a strong gradient in chemical erosion yield along the target.

show abstract

Dissociative Charge Transfer of Argon Ions with Methane Molecules from Ultralow to Superthermal Collision Energies

Cited by 13 publications

References 15 publications

Reactions of State-Selected Atomic Oxygen Ions O⁺(⁴S, ²D, ²P) with Methane

Reactions of State-Selected Atomic Oxygen Ions O⁺(⁴S, ²D, ²P) with Methane

Kinetics and Product Branching Fractions of Reactions between a Cation and a Radical: Ar⁺ + CH₃ and O₂⁺ + CH₃

Carbon transport and escape fraction in a high density plasma beam

Contact Info

Product

Resources

About

Dissociative Charge Transfer of Argon Ions with Methane Molecules from Ultralow to Superthermal Collision Energies

Cited by 13 publications

References 15 publications

Reactions of State-Selected Atomic Oxygen Ions O+(4S, 2D, 2P) with Methane

Reactions of State-Selected Atomic Oxygen Ions O+(4S, 2D, 2P) with Methane

Kinetics and Product Branching Fractions of Reactions between a Cation and a Radical: Ar+ + CH3 and O2+ + CH3

Carbon transport and escape fraction in a high density plasma beam

Contact Info

Product

Resources

About

Reactions of State-Selected Atomic Oxygen Ions O⁺(⁴S, ²D, ²P) with Methane

Reactions of State-Selected Atomic Oxygen Ions O⁺(⁴S, ²D, ²P) with Methane

Kinetics and Product Branching Fractions of Reactions between a Cation and a Radical: Ar⁺ + CH₃ and O₂⁺ + CH₃