RAINBOW SCATTERING OF METHANE FROM LIF(100) - PROBING THE CORRUGATIONAND ANISOTROPY OF THE GAS-SURFACE POTENTIAL

We have used high-resolution infrared laser spectroscopy and optotherm al detection to investigate the scattering of methane from LiF(100). T he angular, translational, and rotational distributions of the scatter ed molecules are reported as a function of incident energy, surface te mperature, and incident angle. The results show structured angular dis tributions that can be understood in terms of rainbow scattering, prov iding information on the surface corrugation appropriate to methane, a s well as insights into the energy transfer between the methane and th e surface. In addition, the energy dependence of the rainbow scatterin g, together with the rotational distributions, provide insights into t he molecular anisotropy at both long and short ranges. The experimenta l results are compared with those of the washboard model for rainbow s cattering [J. C. Tully, J. Chem. Phys. 92, 680 (1990)]. (C) 1998 Ameri can Institute of Physics.