Competition of different scattering channels in electron impact vibrational excitation of thin solid films of sulfur hexafluoride

Vibrational high-resolution electron energy loss spectra of solid films of SF6 have been recorded at incident energies (E0) ranging from 1.5 to 16.5 eV. All possible vibrations of SF6 are observed. The spectra reveal characteristic variations of the vibrational band intensities as a function of E0. In addition, an analysis of the multiple scattering spectral region using intensity ratios predicted by a simple multiple scattering model is applied to locate overtone and combination bands. In agreement with earlier gas phase results, the characteristic energy dependence of the intensity of the totally symmetric vibration ν1 gives evidence for three different resonant scattering processes. The energy dependence of the strong dipole scattering band ν3 closely follows the behavior of the elastic intensity that is characterized by minima at approximately the positions of the resonance maxima. This is explained by competing dipole and resonant scattering channels.