The determination of complex refractive indices with fourier-transform interferometry—V. Methods for the determination of complex refractive index spectra of liquids in the far infrared spectral region (5–500 cm −1) using a variable pathlength, variable temperature cell

Abstract

Several methods are given for the determination of complex refractive index spectra n̆ s(σ), where σ is the wavenumber, of transparent as well as very absorbing liquids in the FIR (5–500 cm −1), from dispersive interferograms obtained with a Michelson interferometer of which the fixed-mirror arm is terminated by a variable pathlength, variable temperature cell. The liquid specimen is confined between a displaceable mirror and a fixed plane-parallel window (of e.g. hyperpure silicon, crystal quartz). The complex refractive index spectrum of the window of which a knowledge is required in most of the methods for determining n̆ s(σ), is determined from an empty-cell interferogram. The cell and the interferometric setup are briefly described. Some experimental results are given (silicon, chlorobenzene, methanol).