Received 28 March 2006; revised manuscript received 3 October 2006; published 27 November 2006Reflectance anisotropy spectra RAS , extended into the near infrared spectral region, of anisotropic metalislands, metal surfaces, and atomic nanowires are analyzed with respect to anisotropies in the optical responseof the free-electron gas of such low dimensional metal structures. In order to distinguish conductivity andmorphology effects, both a phenomenological anisotropic Drude model and an effective medium model usingellipsoidal metal inclusions are used to model the spectra. In some cases metal islands the RAS response isdominated by the free-electron contribution, while this contribution is significantly smaller for the metalsurfaces and nanowires in the accessible spectral range.DOI: 10.1103/PhysRevB.74.195432 PACS number s : 73.50. h, 73.20.At, 73.63.Nm, 73.25. i