Strong contributions from surface electromagnetic fields to angle-resolved photoemission intensities of copper

Abstract

Unexpected high photoemission intensity is observed on copper surfaces at grazing incidence angles of p-polarized light $(\ensuremath{\Elzxh}\ensuremath{\omega}=21.2\mathrm{eV}).$ The dipole approximation in combination with Fresnel's equations and the optical constants of copper is not sufficient to explain the experimental data. Instead, local electric-field effects at the surface have to be taken into account. In order to model the observed dependence of intensity on light incidence angle, we follow two different approaches: one using modified optical constants at the surface, and one including surface photoemission. Within both formulations excellent fits to our experimental intensities can be obtained, however, with the present data we cannot decide which model is more appropriate.