ELECTRON-IMPACT SPECTROSCOPY OF SIF4 AND GEF4

Electron energy loss spectra (EELS) of SiF4 and GeF4 have been recorde d by using incident electrons with energy of 200 eV at scattering angl es of about 0-9-degrees. The energy loss range of 10-30 eV covers the entire region of single-electron excitation from the five outer valenc e orbitals of both molecules. The spectra were obtained under conditio ns that favor the observation of both optically allowed and symmetry f orbidden transitions. Evidence is presented for the existence of optic ally forbidden transitions in both molecules as well as excitations to valence as opposed to Rydberg states.