MEASUREMENT OF THE COMPLEX REFRACTIVE-INDEX OF LIQUIDS IN THE INFRARED USING SPECTROSCOPIC ATTENUATED TOTAL-REFLECTION ELLIPSOMETRY - CORRECTION FOR DEPOLARIZATION BY SCATTERING

With spectroscopic ellipsometry one can measure the real and imaginary parts of the refractive index of a medium simultaneously. To determin e this index in the infrared for a number of technical liquids, use wa s made of attenuated total internal reflection at the glass-liquid int erface of a specially designed prism. This attenuated total reflection approach warrants minimal signal loss and is, for strongly absorbing liquids, the only way to measure the complex refractive index. A surpr ising phenomenon, observed when BK-7 prism glass was used, is scatteri ng in the vicinity of the absorption wavelengths of the glass. A simpl e model that can be used to describe the relations among absorption, s cattering, and depolarization was successfully used to correct the mea surements. Refractive indices for demineralized water, Freon 113, hept ane, benzene, gas oil, and crude oil in the wave number range from 500 0 to 10,000 cm(-1)(1-2 mu m) are presented.