Classical theory for scattering of rigid molecules from surfaces

A theoretical model is presented for the scattering of molecules from surfaces under conditions in which the major modes of energy transfer are multiple phonon excitation at the surface and rotational excitations of the molecule. Beginning from a completely quantum mechanical formalism, the classical limit is obtained for large mass molecules and large energies and in this limit the result is a closed-form expression for the scattering intensities. Results of calculations are compared with recent measurements for the scattering of hyperthermal beams of C2H2 from a LiF(0 0 1) surface. The results of these comparisons indicate that a classical theoretical treatment of translational and rotational motion is adequate for describing this system. (C) 2002 Elsevier Science B.V. All rights reserved.