EFFECT OF THE STRUCTURAL ANISOTROPY AND LATERAL STRAIN ON THE SURFACEPHONONS OF MONOLAYER XENON ON CU(110)

The phonon-dispersion curves for a xenon monolayer adsorbed on Cu(110) have been measured using inelastic He scattering. The size and geomet ry of the substrate unit cell introduces an anisotropic distortion of the xenon monolayer, which is reflected in a strong deformation of the phonon-dispersion curves with respect to the floating two-dimensional (2D) xenon layer. This effect is reproduced in a 2D phonon calculatio n, based on the Lennard-Jones Xe pair potential. In this way a microsc opic relationship between lattice strain, force constants, and surface stress can be established.,