Electron attachment to 14 halogenated alkenes and alkanes, 300-600 K

Abstract

Thermal electron attachment to 14 alkenes and alkanes with bromine, fluorine, and iodine substituents has been studied over the temperature range 300-600 K using a flowing-afterglow Langmuir-probe apparatus. Rate coefficients and anion products are reported, most for the first time. Among these were 3 isomers of C(3)F(5)Br and the 2 isomers of C(3)F(7)I. Four dibromide compounds were studied, all of which yield Br(2)(-) product in addition to Br(-) product. The results are analyzed using a statistical kinetic modeling approach, which is able to reproduce both attachment rate coefficients and product branching ratios within experimental uncertainty. The kinetic modeling indicates that factor of 2 differences in attachment rate coefficients to the isomeric species can be explained by subtle variations in the potential surfaces.

Electron attachment to CF3 and CF3Br at temperatures up to 890 K: Experimental test of the kinetic modeling approach

“…The latter measurements fall slightly (∼10%) below recently published values by our group using the same method and apparatus; 16 an average of the current and prior measurements is reported here. Attachment is exclusively dissociative yielding Br − , and is increasingly efficient as the temperature approaches 1000 K, about the point at which CF 3 Br thermally decomposes.…”

“…6,[9][10][11] Over the past several years an alternative approach of applying kinetic modeling to an attaching system has been developed, [12][13][14] with continued success in replicating experimental results. 11,15,16 As opposed to first-principles approaches, kinetic modeling involves only simple calculation and requires only modest information of the potential energy surface. The approach is to reduce the attachment process as a) Author to whom correspondence should be addressed.…”

Reactions of C+ + Cl−, Br−, and I−—A comparison of theory and experiment

“…In this work, CCl N , CF E Br E , and C E F @ I were the neutral precursors used to make the atomic halide anions Cl & , Br & , and I & , respectively. 38,39 All flows were metered using mass flow controllers (MKS Instruments). Ions on the axis of the flow were sampled through a 330-µm aperture in a truncated nosecone at the downstream end of the flow tube.…”

Dissociative recombination and mutual neutralization of heavier molecular ions: C10H8+, WF5+, and CnFm+

“…For MN measurements, CCl 4 , CF 2 Br 2 , or C 2 F 3 I was added to the flow tube through a glass inlet to rapidly convert electrons to the anions Cl − , Br − , or I − via dissociative electron attachment. 38,39 All reactant gases were prepared as ∼1% mixtures in He (99.999%, Matheson) and introduced through the same inlet as the anion precursors. WF 6 was obtained as a gas from Syn-Quest Laboratories, Inc. C 7 F 14 was obtained from SynQuest Laboratories, Inc., at a stated purity of 95%; the liquid was degassed using freeze-pump-thaw and the vapor diluted in He.…”