Experimental and theoretical evidence for a strong anisotropy of the surface Debye-Waller factor as determined for a monolayer of cobalt on copper(111) by surface extended X-ray-absorption fine structure

The first determination of the anisotropy of the surface Debye--Waller factor involved in a surface extended X-ray-absorption fine-structure (SEXAFS) experiment is presented. It is deduced by use of relative temp.-dependent amplitude functions for two different polarizations. The mean square relative displacements of atoms are calculated with an elaborate lattice-dynamical model, treated by a continued-fraction technique. The results are in good agreement which shows the ability of SEXAFS as a valuable tool for the study of surface vibrations. 17 ref.--AA