INELASTIC RAINBOW SCATTERING OF CH4 MOLECULES FROM A LIF(001) SURFACE

Angular intensity and velocity distributions of CH4 scattered from a L iF(001) surface have been measured using CH4 molecular beams with ener gies in the range of E-i = 190-570 meV. Rainbow scattering of CH4 mole cules has been obtained for the [100] incident azimuthal direction and the results are compared with the ''Washboard'' model proposed by Tul ly [J. Chem. Phys. 92 (1990) 680]. A qualitative agreement between our experimental results and the model has been observed as far as the de pendence of angular intensity distribution of scattered CH4 molecules on both incident energy and surface temperature are concerned. It is f ound that the attractive potential acting on CH4 at the LiF surface pl ays an important role in determining the rainbow peak position. The mo del also explains the angular velocity distribution of scattered CH4 m olecules.