SURFACE PHOTOEMISSION IN AG(100)

Photoemission from the sp band of Ag(100) is significantly affected by surface effects. The dominant surface contribution at low-photon ener gies is derived from a del . A term in the optical-transition matrix e lement which gives rise to a significant amplitude for indirect transi tions. This surface term interferes with the usual momentum matrix ele ment for band-to-band transitions in the bulk, resulting in an asymmet ric direct-transition peak. A line-shape analysis of spectra taken wit h various photon energies leads to a quantitative determination of thi s surface contribution. The results, as well as similar results for Ag (lll) obtained over a different but adjoining range of photon energy, will be compared with the photon energy dependence of the dielectric f unction of Ag.