Inelastic electron scattering of surface and bulk phonons on Cu(001)-p(2×2)S

We have studied the scattering of electrons by surface and bulk phonons from the $p(2\mathrm{}\times 2)\mathrm{S}$ on Cu(001) system. We find four surface phonons and a group of overlayer-induced bulk modes that produce larger electron-phonon loss cross sections. Comparison between microscopic theory and experiment indicates that the S adsorption distance is 1.30±0.05 Å above the fourfold hollow site.