Surface effects on the x-ray photoemission spectra of metals

The effects of the presence of the surface on the main line shape and strength of the photoemission spectra of metals and adsorbates have been investigated. By using a modified Nozières-deDominicis theory, recently developed by Bose, Kiehm, and Longe for the bulk photoemission spectra of metals, the power-law exponent $\alpha$ and the intensity parameter $\xi$ have been calculated as functions of $z_0$, the distance from the surface. With the use of these values, the asymmetry indices at half- and quarter-maxima, as well as the maximum intensities, have been calculated. These quantities are seen to be highly influenced by the presence of the surface for photoemission from adsorbate atoms outside the sample. The surface has moderate effects on the photoemission from atoms embedded inside the sample. The results obtained in this article can be utilized to estimate the distance of a photoemitting adsorbate atom, from the experimentally observed asymmetry indices and intensity maxima.