LINESHAPES OF SURFACE-INDUCED OPTICAL ANISOTROPY SPECTRA MEASURED BY RDS RAS/

In this paper we discuss lineshapes of reflectance-difference spectros copy (RDS/RAS) spectra of various surfaces. This work aims toward a ba sic understanding of the surface optical response. We find that in som e cases RDS spectra are given by the bulk dielectric function or its e nergy derivative. In the former case screening effects such as the sur face local field effect are dominant. In the latter case the surface m odifies the bulk electronic structures and we find that the excited st ates must be localized near the surface. Even in the simplest case whe re 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. (C) 1998 Elsevier Science B.V.