Absolute partial cross sections for the parent ionization of the CF x (x=1-3) free radicals by electron impact

V. Tarnovsky, K. Becker

Research output: Contribution to journalArticle

Abstract

We report absolute partial electron-impact ionization cross sections from threshold to 200 eV for the formation of the parent CFx + ions from the CFx free radicals (x=1-3). Fast (3-3.5 kV) beams of CF3, CF2, and CF radicals were prepared by near-resonant charge transfer of CF3 +, CF2 +, and CF+ with triethylamine (TEA), Xe, and NF3. The CF and CF3 neutral beams were found to contain primarily ground state neutral radicals with some evidence for the presence of a small amount of vibrational excitation (0.5 eV or less). Contributions to the CF 2 + ion signal obtained at electron energies several electron volts below the 11.4 eV threshold for the ionization of ground state CF2 radicals indicate the presence of CF2 metastables (presumably in the 3B1 state) in the CF2 neutral beam. The level of CF2 metastable contamination was found to depend critically on the exact experimental conditions. At 70 eV, the absolute parent ionization cross sections are 0.38±0.07 Å2 (CF3→CF3 +), 1.03±0.16 Å2 (CF2→CF2 +), and 1.25±0.19 Å2 (CF→CF+), respectively.

Original languageEnglish (US)
Pages (from-to)7868-7874
Number of pages7
JournalThe Journal of chemical physics
Volume98
Issue number10
StatePublished - 1993

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free radicals
electron impact
Free Radicals
Ionization
neutral beams
ionization cross sections
ionization
Ground state
Electrons
cross sections
Ions
Impact ionization
ground state
thresholds
Charge transfer
ions
contamination
Contamination
charge transfer
electron energy

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

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Absolute partial cross sections for the parent ionization of the CF x (x=1-3) free radicals by electron impact. / Tarnovsky, V.; Becker, K.

In: The Journal of chemical physics, Vol. 98, No. 10, 1993, p. 7868-7874.

Research output: Contribution to journalArticle

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abstract = "We report absolute partial electron-impact ionization cross sections from threshold to 200 eV for the formation of the parent CFx + ions from the CFx free radicals (x=1-3). Fast (3-3.5 kV) beams of CF3, CF2, and CF radicals were prepared by near-resonant charge transfer of CF3 +, CF2 +, and CF+ with triethylamine (TEA), Xe, and NF3. The CF and CF3 neutral beams were found to contain primarily ground state neutral radicals with some evidence for the presence of a small amount of vibrational excitation (0.5 eV or less). Contributions to the CF 2 + ion signal obtained at electron energies several electron volts below the 11.4 eV threshold for the ionization of ground state CF2 radicals indicate the presence of CF2 metastables (presumably in the 3B1 state) in the CF2 neutral beam. The level of CF2 metastable contamination was found to depend critically on the exact experimental conditions. At 70 eV, the absolute parent ionization cross sections are 0.38±0.07 {\AA}2 (CF3→CF3 +), 1.03±0.16 {\AA}2 (CF2→CF2 +), and 1.25±0.19 {\AA}2 (CF→CF+), respectively.",
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N2 - We report absolute partial electron-impact ionization cross sections from threshold to 200 eV for the formation of the parent CFx + ions from the CFx free radicals (x=1-3). Fast (3-3.5 kV) beams of CF3, CF2, and CF radicals were prepared by near-resonant charge transfer of CF3 +, CF2 +, and CF+ with triethylamine (TEA), Xe, and NF3. The CF and CF3 neutral beams were found to contain primarily ground state neutral radicals with some evidence for the presence of a small amount of vibrational excitation (0.5 eV or less). Contributions to the CF 2 + ion signal obtained at electron energies several electron volts below the 11.4 eV threshold for the ionization of ground state CF2 radicals indicate the presence of CF2 metastables (presumably in the 3B1 state) in the CF2 neutral beam. The level of CF2 metastable contamination was found to depend critically on the exact experimental conditions. At 70 eV, the absolute parent ionization cross sections are 0.38±0.07 Å2 (CF3→CF3 +), 1.03±0.16 Å2 (CF2→CF2 +), and 1.25±0.19 Å2 (CF→CF+), respectively.

AB - We report absolute partial electron-impact ionization cross sections from threshold to 200 eV for the formation of the parent CFx + ions from the CFx free radicals (x=1-3). Fast (3-3.5 kV) beams of CF3, CF2, and CF radicals were prepared by near-resonant charge transfer of CF3 +, CF2 +, and CF+ with triethylamine (TEA), Xe, and NF3. The CF and CF3 neutral beams were found to contain primarily ground state neutral radicals with some evidence for the presence of a small amount of vibrational excitation (0.5 eV or less). Contributions to the CF 2 + ion signal obtained at electron energies several electron volts below the 11.4 eV threshold for the ionization of ground state CF2 radicals indicate the presence of CF2 metastables (presumably in the 3B1 state) in the CF2 neutral beam. The level of CF2 metastable contamination was found to depend critically on the exact experimental conditions. At 70 eV, the absolute parent ionization cross sections are 0.38±0.07 Å2 (CF3→CF3 +), 1.03±0.16 Å2 (CF2→CF2 +), and 1.25±0.19 Å2 (CF→CF+), respectively.

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