Threshold Electron-Impact Excitation and Negative-Ion Formation in XeF6 and XeF4

Electronic excitation and dissociative electron attachment in XeF6 and XeF4 were investigated by studying the products of low-energy electron–molecule collisions in the gas phase. The relative abundances of the major negative ions produced were recorded as a function of the electron-beam energy. Both molecules attached electrons at ∼0 and ∼5 eV and dissociated into a number of negative-ion products. The similar energy dependence of the various ion currents suggested that the fragment ions were competing for the electron attached to XeF6 or XeF4. The threshold electron-impact excitation spectra were determined by means of the “SF6-electron-scavenger” technique. No evidence for low-lying electronic states was found.