Electron-impact excitation of methane, silane, tetrafluoromethane and tetrafluorosilane has been explored in a trapped-electron spectrometer. Extensive vibrational excitation of CF4 was observed with electrons of very low incident energies. There was some evidence of multiple vibrational excitation in SiH4 also but the results for this molecule were not totally unambiguous. Nearthreshold vibrational excitation of SiF4 was masked by effects attributed to a large cross-section for elastic scattering. Some optically forbidden electronic states have been located and assignments suggested. Short-lived negative-ion states (resonances) affect electronic excitation of the lowest excited Rydberg state in SiH4, CF4 and SiF4 as well as negative-ion production.
|Number of pages
|Journal of the Chemical Society, Faraday Transactions 2: Molecular and Chemical Physics
|Published - 1989