Optical properties and excitation energies of iridium derived from reflection electron energy loss spectroscopy spectra

Abstract

We present the combined experimental and theoretical investigations of optical properties and excitation energies of metallic iridium. The reflected energy loss spectroscopy (REELS) spectra of polycrystalline Ir were measured with a cylindrical mirror analyzer in UHV conditions at primary energies of 500, 1000 and 2000 eV. The energy loss function (ELF) and thereby the refractive index n and the extinction coefficient k were calculated from these REELS spectra in the loss energy range of 2–200 eV by applying our reverse Monte Carlo method. The high accuracy of the obtained results is justified with the ps- and f-sum rules. Using the derived ELF the inelastic mean free paths of Ir were calculated from 1 eV up to 10 keV. Moreover, we identified for the first time in the optical data the 5p3/2, 4f5/2 and 4f7/2 shell excitations of the solid Ir sample.