Different Core-Hole Lifetime and Screening in the Surface of W(110)

We report the first determination of the modification in the core-hole lifetime and many-body screening exponent in the first atomic layer of a metal. The experiments were done on the (110) face of a single-crystal W ribbon [1], which was cleaned by standard techniques in a base pressure of 1X10 sup (-10) Torr. For this surface, The second atomic layer has the same nearest- and next- nearest-neighbor coordination as the atoms in the bulk. The work was carried out on the AT&T Bell Laboratories 6m TGM on the VUV ring of the National Synchrotron Light Source at Brookhaven National Laboratory [2]. The measurements were made with a VSW 100mm hemispherical analyzer. Combined with that of the TGM, the total instrumental resolution was better than 85 meV.