HIGH-RESOLUTION HELIUM SCATTERING STUDIES OF INELASTIC INTERFERENCE STRUCTURES OF THE FRUSTRATED TRANSLATIONAL MODE OF CO ON CU(001)

The angular distributions of multiquantum excitations of the lowest en ergy, frustrated translational vibrations of a low coverage of CO chem isorbed on Cu(001) have been investigated by high resolution helium sc attering time-of-flight measurements. The elastic and the one-phonon c reation and annihilation cross sections show several interference undu lations as a function of parallel momentum transfer, and up to four mu ltiquantum overtones. All the experimental observations are in reasona ble agreement with a multiquantum scattering theory, which also provid es information on the height and width of the adsorbed CO molecules.