Collision induced dissociation, proton abstraction, and charge transfer for low energy collisions involving CH4+

Abstract

Integral and differential cross section measurements at low collision energies for the N 2 + + CH 4 / CD 4 reactions Measurements of total cross sections for collision induced dissociation, proton abstraction, and charge transfer have been made for collisions of CH 4 ϩ with CD 4 , H 2 , and Ar. The laboratory collision energies range from a few up to 400 eV, and isotopic substitutions have been made where possible to investigate any possible isotope effects, and for some reactants, to more closely identify the product ions. Cross sections for all reaction channels are observed to be small; Շ5 Å 2 for the methane target, Շ0.5 Å 2 for the hydrogen target, and Շ2 Å 2 for the argon target. For the methane and hydrogen targets, proton abstraction is observed at low energies while charge transfer occurs for energies տ10 eV. The implications of internal energy present in the CH 4 ϩ projectile for the cross section measurements is discussed. In addition, decomposition of CD 4 H ϩ is addressed in terms of recent calculations related to the structure of the CH 5 ϩ ion.

Hydrocarbon σ‐radical cations

“…In the gas phase, the most favorable intramolecular reaction of CH 4 •+ 67 is the formation of methyl cation CH 3 + where the dissociation threshold is 14.3 eV and where the electron depleted CH bond is very weak (the BDE in H·CH 3 •+ is only 39 kcal/mol) 68. The formation of the methyl radical through the intermolecular CH 4 •+ + CH 4 → CH 5 + + CH 3 • collision reaction is −0.2 eV exothermic and was observed experimentally in the gas phase 69…”

Selective Alkane Transformations via Radicals and Radical Cations: Insights into the Activation Step from Experiment and Theory

“…816 Formation of the methyl radical through the intermolecular CH 4 •+ + CH 4 f CH 5 + + CH 3 • collision reaction is -0.2 eV exothermic. 817 Methane activation with strong electrophiles is one of the major achievements of superacid chemistry. 18,165 The original mechanistic rationalization is based on the direct attack of the electrophile on the C-H bonds.…”

“…The most favorable intramolecular gas-phase reaction of CH 4 •+ 815 is the formation of the methyl cation CH 3 + : the ion dissociation threshold is 14.3 eV, and the BDE for the (H−CH 3 ) •+ is 1.7 eV . Formation of the methyl radical through the intermolecular CH 4 •+ + CH 4 → CH 5 + + CH 3 • collision reaction is −0.2 eV exothermic …”

An investigation of plasma chemistry for dc plasma enhanced chemical vapour deposition of carbon nanotubes and nanofibres

“…This is especially true in nanotube processing where sheaths are collisional because of higher operating pressures (∼10 mbar) and ion energies are significant because of the large applied biases (∼500 V) required for alignment such that both exothermic and endothermic ion-molecule reactions are important. these reactions for methane from the work of Peko et al [56] were used as estimates for acetylene and ammonia, where the experimentally measured cross-sections reported for these reactions were integrated over a Maxwellian distribution and then fitted to the Arrhenius form.…”