Immersion Spectrophotometry of Interference Films: Refractive Indices of Fluoride Films on Uranium Dioxide and Anodic Oxide Films on Uranium Metal*

Abstract

The principles of the immersion spectrophotometry of interference films are discussed. A practical application is presented for determining directly the refractive indices of thin films in situ on solid substrates. With this method the spectrophotometric peak heights are measured with the specimen immersed in various fluids. The plot of peak height vs index of refraction of the immersion medium is a smooth line going through zero at the refractive index of the interference layer. The mathematical basis of the method is developed and data for fluoride films on uranium dioxide and for anodic oxide films on uranium metal are presented.