Adsorbate-induced changes in the infrared reflectance and resistivity of metals

We present an experimental test of a predicted relationship between adsorbate-induced changes in the infrared reflectance and dc resistivity of a metal. We have measured the absolute change in reflectance for O and CO on Cu(100) and for CO on Ni(100) over the frequency range 300–2000 ${\mathrm{cm}}^{\mathrm{-}1}$ and compared it with published resistivity changes for the corresponding thin-film systems. For the two adsorbates on Cu the results are consistent with a simple model based on scattering of conduction electrons by the adsorbate. For CO on Ni, however, the reflectance change is much smaller than predicted.