The infrared refractive indices of CHBr3, CCl4 and CS2

Abstract

Spectrally resolved data for the real part, n(λ) of the complex refractive index, $\text{n}\text{̂}\text{= n +}\text{i}\text{k}$, of bromoform (tribromomethane, CHBr₃) at room temperature (298 K) in the wavelength range 1–13 μm are presented. The measurements were made using the near-normal reflectance technique. The accuracy of the method was confirmed by comparing measured values of n(λ) of water with available data in the literature. For bromoform, n(λ) is found to decrease gradually from 1.58 to 1.51 over this wavelength range, except in the region of anomalous dispersion near absorption bands at 3.3 and 8.7 μm. A complete infrared window for extinction measurements on suspended particulates can be obtained using CCl₄ in the spectral range 1–6 μm, CHBr₃ in the ranges 6.0–7.4 μm and 11–13 μm, and CS₂ in the range 7.4–11.0 μm. The data for n(λ) of CCl₄ in the range 1–9 μm, and those for CS₂ in the range 7.4–11.0 μm, obtained from reflectance measurements, compare favorably with data available in the literature.