Theory of 45 degrees reflectometry from metal surfaces

The use of optical spectroscopies to study surfaces is hindered by the diff iculty of disentangling bulk and surface contributions to the signal. Accor ding to Fresnel formulae, the a and p reflectances R of a semi-infinite sys tem obey the simple relation Delta = R-s(2) - R-p = 0 when the incidence an gle is 45 degrees. Deviations from this result can be related to microscopi c surface contributions to R. In this paper we study theoretically Delta fo r metal surfaces. For a semi-infinite nat jellium we obtain the contributio ns to Delta from electronic excitations at the surface. To explore Delta fo r non-jellium conductors, we apply a 'Swiss cheese' model to different surf aces of Ag.