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Benchmark Cross Sections for Low-Energy Electron Attachment to Molecules with Well-Defined Internal Temperature M. Braun, S. Marienfeld, M.-W. Ruf, and H. Hotop Fachbereich Physik Using two variants of the laser photoelectron attachment method [1] we have measured (relative) cross sections for low-energy electron attachment to the molecules SF6 (formation of SF6-, SF5-, and F-), CCl4 (Cl- formation) and CF3I (I- formation) in a diffuse gas target with well-defined temperature (TG = 300 K) from 0 eV up to 2 eV (electron energy width 1 – 2 meV for E < 200 meV and about 30 meV for E > 200 meV). Absolute cross sections have been established with reference to reliable rate coefficients, obtained consistently by several groups at equal electron and gas temperature (Te = TG = 300 K) [2]. At energies above 0.2 eV, our cross sections exhibit substantial deviations from recommended values [3-5]. For SF6 and CCl4 these differences can be attributed to the fact that in most of the earlier electron beam experiments the gas temperature was higher than 300 K. For CF3I the previously recommended attachment cross sections are too high by at least a factor of five for energies above 0.1 eV. This work has been supported by the Deutsche Forschungsgemeinschaft and
by Forschungszentrum Optische Technologien und Lasergesteuerte Prozesse. References |
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