A Polycrystalline Thin-Film Technique for Infrared Transmission Studies of Alkali Halogenates

Polycrystalline thin films of alkali halogenates have been prepared by a solvent-evaporation technique. Refinement of the technique has enabled us to produce a uniform thin film free of the Christiansen effect. The film thicknesses have been measured by x-ray fluorescence to be from 0.4 to 1.0 µ, with an estimated error of less than 2%. The technique is based on the deposition of a thin film on a high-density polyethylene substrate making it possible to study quantitatively the external vibrational modes and those internal modes of potassium and sodium halogenates which have a resonant frequency of less than 600 cm⁻¹.