Faculté des sciences

Low-energy electron attachment to the dichlorodifluoromethane (CCl₂F₂) molecule

Graupner, K. ; Haughey, S. A. ; Field, T. A. ; Mayhew, C. A. ; Hoffmann, T. H. ; May, Olivier ; Fedor, Juraj ; Allan, Michael ; Fabrikant, Ilya I. ; Illenberger, E. ; Braun, M. ; Ruf, M.-W. ; Hotop, Hartmut

In: The Journal of Physical Chemistry A, 2010, vol. 114, no. 3, p. 1474–1484

Results from a joint experimental study of electron attachment to dichlorodifluoromethane (CCl₂F₂) molecules in the gas phase are reported. In a high resolution electron beam experiment involving two versions of the laser photoelectron attachment method, the relative cross section for formation of the dominant anion Cl⁻ was measured over the energy range 0.001−1.8 eV at the gas... Plus

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    Summary
    Results from a joint experimental study of electron attachment to dichlorodifluoromethane (CCl₂F₂) molecules in the gas phase are reported. In a high resolution electron beam experiment involving two versions of the laser photoelectron attachment method, the relative cross section for formation of the dominant anion Cl⁻ was measured over the energy range 0.001−1.8 eV at the gas temperature TG = 300 K. It exhibits cusp structure at thresholds for vibrational excitation of the ν₃(a₁) mode due to interaction with the attachment channels. With reference to the thermal attachment rate coefficient k(T = 300 K) = 2.2(8) × 10⁻⁹ cm³ s⁻¹ (fitted average from several data), a new highly resolved absolute attachment cross section for TG = 300 K was determined. Partial cross sections for formation of the anions Cl⁻, Cl₂⁻, F⁻, ClF⁻, and CCl₂F⁻ were measured over the range 0−12 eV, using three different electron beam experiments of medium energy resolution. The dependence of the attachment rate coefficient k(Te;TG = 300 K) on electron temperature Te was calculated over the range 50−15000 K, based on a newly constructed total cross section for anion formation at TG = 300 K. R-matrix calculations for Cl⁻ production have been carried out for comparison with the experimental data. The R-matrix results are in line with the main experimental observations and predict the dependence of the DEA cross section on the initial vibrational level ν₃ and on the vibrational temperature. Furthermore, the cross section for vibrational excitation of the ν₃ mode has been computed.