AbstractThe dielectric function of Au films is determined ellipsometrically in the wave‐number ranges 700 cm−1≦v≦ 1900 cm−1and 2500 cm−1≦v≦ 3000 cm−1as well as for 8900 cm−1≦v≦ 32300 cm−1(1.1 eV ≦ ħω ≦ 4 eV). The spectra are discussed taking into account intra‐ and interband transitions. An energy‐dependent plasma frequency and damping is found. The sample effects are essentially described within an effective medium approximation assuming the influence of voids. Some peculiarities of the frequency dependence of the damping parameter are like