Low-Energy Electron Attachment to the Dichlorodifluoromethane (CCl2F2) Molecule

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 114; no. 3; pp. 1474 - 1484
• Main Authors: Graupner, K, Haughey, S. A, Field, T. A, Mayhew, C. A, Hoffmann, T. H, May, O, Fedor, J, Allan, M, Fabrikant, I. I, Illenberger, E, Braun, M, Ruf, M.-W, Hotop, H
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 28.01.2010
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp9081992

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 T G = 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 T G = 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(T e;T G = 300 K) on electron temperature T e was calculated over the range 50−15 000 K, based on a newly constructed total cross section for anion formation at T G = 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.