The Infra-red Properties of Some Metallic Films

Abstract

The values of the refractive index n and the extinction coefficient k have been measured for evaporated films of gold, silver, copper, zinc, tin and aluminium, at wavelengths between 1 and 15 μ, by a reflection method. The apparatus for the measurements contained two selenium film polarizers, and an infra-red spectrometer with two rock salt prisms and a radiation thermocouple. Theoretical formulae for the infra-red properties of a metal are discussed and it is shown that the present experimental results are not sufficiently accurate to distinguish between the classical free election theory and later modifications. The experimental results have been compared with theory by a graphical method. Some inferences about electronic band structures are made from the comparison of experimental points with theoretical curves.