New measurements are reported of the optical constants of Cu, Ag, and Au in the range 3 to 19 µ. It is shown that the experimental data can be used to discriminate between the various theories on which their interpretation may be based. The present results are most closely related to the anomalous skin-effect theory, with diffuse reflection of electrons.
A. P. LENHAM and D. M. TREHERNE, "Applicability of the Anomalous Skin-Effect Theory to the Optical Constants of Cu, Ag, and Au in the Infrared," J. Opt. Soc. Am. 56, 683-685 (1966)