Electron attachment and detachment: C{sub 6}F{sub 5}Cl, C{sub 6}F{sub 5}Br, and C{sub 6}F{sub 5}I and the electron affinity of C{sub 6}F{sub 5}Cl

Journal Article · Sat Jan 01 00:00:00 EST 2005 · Physical Review. A

DOI:https://doi.org/10.1103/PhysRevA.71.012702· OSTI ID:20650231

Miller, Thomas M; Viggiano, A A ^[1]

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1. Air Force Research Laboratory, Space Vehicles Directorate, Hanscom Air Force Base, Bedford, Massachusetts 01731-3010 (United States)

Measurements are reported of rate constants for electron attachment to C{sub 6}F{sub 5}X (X=Cl,Br,I) and thermal electron detachment from C{sub 6}F{sub 5}Cl{sup -} over the temperature range 300-550 K in 133 Pa of He gas in a flowing-afterglow Langmuir-probe apparatus. This is the first case we know of where the parent anion has sufficiently low electron detachment energy that detachment (from C{sub 6}F{sub 5}Cl{sup -} in this case) has been observed in competition with a channel for dissociative electron attachment yielding a thermally stable anion (here, Cl{sup -}). Because of this competition, it is shown that a simple mass spectrometric determination of the product branching fractions at long times will lead to erroneous results at elevated temperatures. The electron density profiles provide evidence for a new plasma decay process involving the detaching and nondetaching anions trapped in the space charge field of the positive ions. Electron attachment rate constants were found to be 1.0x10{sup -7}, 1.1x10{sup -7}, and 2.0x10{sup -7} cm{sup 3} s{sup -1}, at 300 K, for C{sub 6}F{sub 5}Cl, C{sub 6}F{sub 5}Br, and C{sub 6}F{sub 5}I, respectively, estimated accurate to {+-}25% except for C{sub 6}F{sub 5}I, where there is {+-}30% uncertainty. Rate constants for C{sub 6}F{sub 5}Cl changed little over our temperature range, while those for C{sub 6}F{sub 5}Br, and C{sub 6}F{sub 5}I increased with temperature. Electron detachment occurred only for C{sub 6}F{sub 5}Cl{sup -} in our temperature range. Detachment rate constants were immeasurable at room temperature but approached 4000 s{sup -1} at 550 K. From these data the electron affinity (EA) for C{sub 6}F{sub 5}Cl was determined, EA (C{sub 6}F{sub 5}Cl)=0.75{+-}0.08 eV. G3(MP2) calculations (based on Moeller-Plesset perturbation theory) were carried out for the neutral and anion and yielded EA(C{sub 6}F{sub 5}Cl)=0.728 eV.

• OSTI ID: 20650231
• Journal Information: Physical Review. A, Vol. 71, Issue 1; Other Information: DOI: 10.1103/PhysRevA.71.012702; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
AFFINITY
AFTERGLOW
ANIONS
BRANCHING RATIO
CATIONS
CHLORINE IONS
DISSOCIATION
ELECTRON ATTACHMENT
ELECTRON COLLISIONS
ELECTRON DENSITY
ELECTRON DETACHMENT
ELECTRON TEMPERATURE
EV RANGE
LANGMUIR PROBE
MASS SPECTROSCOPY
ORGANIC COMPOUNDS
PERTURBATION THEORY
PLASMA
PLASMA DENSITY
REACTION KINETICS
SPACE CHARGE
TRAPPING