NORMAL AND OBLIQUE SPECULAR REFLECTIVITY OF CUGEO3

We report on the ac-plane specular reflectivity of CuGeO3 as a functio n of the angle of incidence. While our spectra for near-normal inciden ce are those of an insulator, in the grazing-incident spectrum we foun d a broad continuum. This suggests that the b-direction response, that is, the response normal to the ac plane, is weakly metallic. We sugge st the origin of this electronic anisotropy is due to impurity levels in the gap. We reason that its presence is due to oxygen vacancies in the chains and that this would justify, at least in part, some of the softening of the longitudinal acoustical mode recently reported by neu tron-scattering measurements.