Attenuated total reflection spectroscopy of liquids using GaP-Raman terahertz spectrometer

We have measured the spectra of liquid water and solutions using widely frequency-tunable terahertz wave generator based on the resonance of the phonon-polaritons in GaP. Although terahertz wave can hardly be transmitted in a liquid water owing to the large absorption coefficient, using attenuated total reflection techniques, terahertz spectra of methanol and glucose in water can be measured. The internal reflectivity of the methanol and water mixture increases with amount of methanol. The frequency dependence of dispersion in the reflection spectra of solutions is thought to be dispersion in the refractive index. Spectral feature could characterize solutes in water.