Measurement and density functional calculations of optical constants of Ag and Au from infrared to vacuum ultraviolet wavelengths

The dielectric function of Ag and Au for wavelengths ranging from the infrared to the vacuum ultraviolet regime was measured with reflection electron energy-loss spectroscopy (REELS). The spectra are compared to density functional theory (DFT) calculations and to experimental optical data available in the literature since about three decades ago. The REELS and DFT results exhibit good consistency, while the earlier optical data significantly deviate. The results demonstrate that REELS and DFT are powerful tools for the study of the electromagnetic response of surfaces.