TY - JOUR
T1 - Absolute partial cross sections for the parent ionization of the CF x (x=1-3) free radicals by electron impact
AU - Tarnovsky, V.
AU - Becker, K.
PY - 1993
Y1 - 1993
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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U2 - 10.1063/1.464594
DO - 10.1063/1.464594
M3 - Article
AN - SCOPUS:0001467098
SN - 0021-9606
VL - 98
SP - 7868
EP - 7874
JO - The Journal of Chemical Physics
JF - The Journal of Chemical Physics
IS - 10
ER -