Effects on Photoemission of the Spatially Varying Photon Field at a Metal Surface

Abstract

Enhancement of photoionization cross sections due to spatially varying photon fields at a metal surface has been observed in the normal-emission cross sections for the surface state and Fermi level of A1(100) at photon energies between 9 eV and 23 eV. The data for Fermi-level photoexcitation are in excellent agreement with theoretical results for jellium. Below $\ensuremath{\hbar}{\ensuremath{\omega}}_{p}$, the predominant contribution to the photoionization matrix element comes from the spatially varying fields, which provide the momentum required for photoexcitation.