VIBRATIONAL-EXCITATION OF CF3BR SCATTERING FROM GRAPHITE

We present results from molecular beam experiments and classical traje ctory calculations on CF3Br scattering from graphite. Direct inelastic scattering dominates for initial translational energies E-tr=0.7-2.5 eV and surface temperatures T-s=830-1170 K. Vibrationally excited mole cules are observed in the scattered flux using the method of electron- induced fragmentation. The vibrational excitation depends on E-tr and T-s, and a maximum temperature increase of 164+/-10 K is reached at E- tr=2.5 eV. Inelastic angular distributions and the vibrational excitat ion are semi-quantitatively reproduced by three-dimensional stochastic trajectory calculations, which indicates that vibrational excitation can be explained by an electronically adiabatic ''mechanical'' process . (C) 1997 Elsevier Science B.V.