VIBRATIONAL-EXCITATION OF SF6 SCATTERING FROM GRAPHITE

We have observed vibrationally excited sulfur hexafluoride molecules i n direct inelastic scattering from hoc graphite surfaces. The vibratio nal temperature for the scattered flux has been determined by probing the effect of internal temperature on electron-induced fragmentation o bserved in mass spectra. The vibrational excitation depends on inciden t translational energy, E(tr), and a maximum temperature increase of 5 0 K is reached in direct scattering at E(tr) = 2.5 eV. No effect of su rface temperature has been observed at 950-1400 K. Inelastic angular d istributions are reproduced by a collision complex model, and the expe rimental results are related to existing models for vibrational excita tion.