CORE-HOLE LIFETIME AND SCREENING ARE DIFFERENT IN THE SURFACE OF W(110)

High resolution 4f photoemission spectra from clean W(110) show that the natural lifetime width and the singularity index, which characterizes the conduction electron screening, are both larger in the first atomic layer than in the bulk. The phonon broadening of the surface and bulk components are smaller than earlier theoretical estimates. The excess broadening at the surface is compatible with a simple Debye model. These findings are very different from the interpretation previously given surface-atom core-level line shapes and have implications extending to other systems. © 1990 IOP Publishing Ltd.