The optical properties of amorphous-diamond films prepared by a mass-separated ion beam are studied and compared with the shape of the corresponding Raman spectra. The Raman measurements with moderate spatial resolution indicate that the films possess thesp3fraction distributed along the film surface, the thinner edges being less diamondlike than the thicker center. The optical parameters of the film material, such as the refractive index and absorption coefficient, follow the spatial changes of thesp3fraction, and the amorphous-diamond center is characterized by a relatively high refractive index(n∼2.50)and quite low absorption(&agr;∼0.2×104 cm−1at 633 nm). Numerical correlation between the Raman spectra and optical parameters proposes a common origin for their spatial distribution, namely, impurities perturbing the three-dimensional diamondlike network and causingsp2-coordinated carbon areas. ©1997 American Institute of Physics.