Photoemission from a Ag(111) surface: Failure of the plane-wave, orthogonalized-plane-wave, and augmented-plane-wave final states

Abstract

Photoemission spectra directed along the (111) axis of Ag for $h\nu =16.8, 21.2, 26.9, 40.8, \mathrm{and} 1254$eV are presented. Simple symmetry considerations are employed to demonstrate that final electron states consisting of a single plane wave, or a combination of plane waves mixed by a weak crystal pseudopotential incorrectly describes the photoemission incorrectly describes the photoemission spectra. It is pointed out that part of the inadequacy of the plane wave is due to its failure to describe the true final state in the region of the atomic cores. Augmented-plane-wave and orthogonalized-plane-wave final states do better than the plane-wave final state, but they predict a vanishing emission for initial states having $m\ge 2$. It is concluded that the above states must be strongly mixed to explain the experimental spectra.