Cu(001) to HD energy transfer and translational to rotational energy conversion on surface scattering

Intense peaks are observed in angular intensity distributions for HD scatte ring from the Cu(001) surface. These can be ascribed to coherent diffractio n with translational energy transfers of DeltaE=0, -11.0, or 33.11 meV to m olecular rotational energy. Time-of-flight spectra, at other scattering ang les, display inelastic peaks that are assigned to phonon creation or annihi lation processes with either the HD rotationally elastic or inelastic trans itions. The HD phonon dispersion curves suggest a strong HD coupling both w ith surface Rayleigh modes and with bulk phonon modes of the metal surface. Comparisons of both elastic and inelastic scattering intensities are also made with those reported for the Ni(001) surface. To explain an apparent an omalous diffraction peak intensity ratio for Ni, a preferential coupling fo r the HD J=0 rotational state into a predissociation channel above the Ni s urface is proposed. (C) 2001 American Institute of Physics.