Electron attachment and detachment and the electron affinity of cyclo-C4F8

Abstract

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A new instrument for thermal electron attachment at high temperature: NF3 and CH3Cl attachment rate constants up to 1100 K

“…ment was repeated for the present work since a number of improvements have been made in the apparatus, notably in the temperature uniformity in the reaction zone. 36 Table I lists results obtained for NF 3 using the new HT-FALP ͑500-900 K͒ apparatus along with the new FALP data ͑300-550 K͒. The agreement between the two sets of data is quite good.…”

Electron Attachment to C7F14, Thermal Detachment from C7F14–, the Electron Affinity of C7F14, and Neutralization of C7F14– by Ar+

“…The major uncertainty comes from the presence of nondetaching anions at high temperatures, which prevents the electron density from reaching a diffusion-limited steady state condition at long reaction time. The electron decay shown in Figure may be compared, for example, with data obtained for c-C 4 F 8 , where the electron density could be measured at the diffusion limit as far as the Langmuir probe could be moved downstream of the reactant inlet (35 cm or 3.5 ms) . If only a parent anion is present and detaching, two parameters fit the data: the initial decay in the electron density is determined by k a and the steady state condition at long reaction time is determined by k d / k a .…”

“…The electron affinity of C 7 F 14 may be determined from the attachment–detachment equilibrium constant, as has been detailed in earlier publications. ,, Briefly, the k d follow a temperature dependence given by italick normald = italick normala italicL 0 ( 273.15 / T ) nobreak0em0.25em⁡ exp [ − false( EA / italick italicT false) − false( italicT normalΔ italicS 0 / italick italicT false) − false( italicH normalT − italicH 0 false) / k T ] In eq , k is Boltzmann’s constant, L 0 is Loschmidt’s number, EA is the electron affinity of C 7 F 14 (at 0 K, by definition), Δ S 0 is the entropy change due to electron attachment, and H T – H 0 is the thermal energy correction needed to reduce the equilibrium constant to 0 K. EA(C 7 F 14 ) may be obtained by solving eq at each temperature, using the measured k a and k d and the calculated entropy and heat capacity terms. The net entropy Δ S 0 is the anion entropy minus that of the neutral and electron.…”

Electron Affinity of trans-2-C4F8 from Electron Attachment−Detachment Kinetics

“…The electron affinity values determined in this work for cis- and trans- 2 - C 4 F 8 can be compared with that found for the cyclic C 4 F 8 isomer. G3(MP2) computations indicate the electron affinity of the cyclic isomer is 143−160 meV smaller than that of either linear 2- C 4 F 8 isomer, i.e., EA( c- C 4 F 8 ) = 0.595 eV . Comparison of the experimentally derived EAs gives the same result; EA( c- C 4 F 8 ) ∼ EA( trans- 2 - C 4 F 8 ) − 160 meV.…”

“…G3(MP2) computations indicate the electron affinity of the cyclic isomer is 143−160 meV smaller than that of either linear 2- C 4 F 8 isomer, i.e., EA( c- C 4 F 8 ) = 0.595 eV . Comparison of the experimentally derived EAs gives the same result; EA( c- C 4 F 8 ) ∼ EA( trans- 2 - C 4 F 8 ) − 160 meV. The smaller electron affinity of c- C 4 F 8 as compared with the linear isomers presumably arises from the decreased stability of the anion caused by increased electron−electron repulsion in the cyclic structure.…”