Negative ion formation through dissociative electron attachment to the group IV tetrafluorides: Carbon tetrafluoride, silicon tetrafluoride and germanium tetrafluoride

摘要

Dissociative electron attachment (DEA) to the group IV tetrafluorides: CF_4, SiF_4 and GeF_4, is reported in the incident electron energy range from about 0 to 14 eV. The F_2 ~- formation from CF_4 is established and the appearance energies (AEs) for F~-, CF_3 ~- and F_2 ~- are determined using a three-point calibration for the energy scale. These are found to be 4.7 ± 0.1 eV, 4.5 ± 0.1 eV and 5.6 ± 0.1 eV, respectively. For SiF_4 the AEs for F~-, SiF _3 ~- and F_2 ~-, through the dominating resonance are found to be 10.2 ± 0.1 eV, 10.2 ± 0.1 eV and 10.3 ± 0.1 eV, respectively. From GeF_4 the molecular ion GeF _4 ~- and the fragments GeF_3 ~-, GeF _2 ~-, GeF~- and F~- are all observed with appreciable intensities, and the F~- production is found to be significantly close to 0 eV incident electron energy. The present findings are compared with earlier experiments and discussed in context to the thermochemistry of the respective processes as well as the nature of the underlying resonances.