DEBYE-WALLER FACTOR IN HE-]CU(001) COLLISIONS REVISITED - THE ROLE OFTHE INTERACTION POTENTIALS

Following the recently accumulated information on the vibrational prop erties of the Cu(001) surface acquired through single- and multiphonon He atom scattering experiments and the concomitant theoretical invest igations, we have re-examined the properties of the Debye-Waller facto r (DWF) characteristic of the He-->Cu(001) collisions using the recent ly developed fully quantal and three-dimensional model of inelastic He atom scattering from surfaces. We have focused our attention on the-r ole which the various He-surface model potentials with their character istic interaction parameters (range of the interaction, momentum and e nergy transfer cut-offs etc.) employed in the interpretation of the sc attering data may play in determining the magnitude of the DWF. By com bining the He-Cu(001) potential, whose repulsive and attractive compon ents are both allowed to vibrate, with the substrate phonon density of states encompassing anharmonic effects, we obtain the values of the D WF which agree nicely with the experimental data without invoking addi tional fitting parameters. In contrast, by taking the phonon momentum transfer cut-off Q(c) as an adjustable parameter, as was frequently ex ploited in the literature, all the considered potentials can produce a greement with experiments by varying Q(c). The magnitudes of such best fit Q(c) values are compared with those available in the literature a nd their physical significance is discussed. (C) 1997 Elsevier Science B.V.