Lineshapes of surface induced optical anisotropy spectra measured by RDS/RAS

In this paper we discuss lineshapes of reflectance-difference spectroscopy (RDS/RAS) spectra of various surfaces. This work aims toward a basic understanding of the surface optical response. We find that in some cases RDS spectra are given by the bulk dielectric function or its energy derivative. In the former case screening effects such as the surface local field effect are dominant. In the latter case the surface modifies the bulk electronic structures and we find that the excited states must be localized near the surface. Even in the simplest case where the anisotropy originates at the surface the optical anisotropy in general depends on the dielectric function of the bulk as well as that of the surface.