Emissivity measurements on noble metals: validation of a free-electron description including the anomalous skin effect

Abstract The optical properties of noble metals (Cu, Ag, and Au) have been studied in the mid-infrared using emissivity measurements at 473 K. Their optical responses can be described using classical free-electron expressions in the Mott–Zener approximation with an additional term to account for the extra emission due to the anomalous skin effect, with no free parameters. Clear differences between the specular and diffuse surface scattering regimes can be observed. These results constitute metrological-quality validations of the thermal radiative properties of these important metals. Graphical abstract