Absorption spectra and index of refraction of aminophenol compounds are obtained using Terahertz time-domain
spectroscopy (THz-TDS) in the frequency range between 0.3 and 2.0 THz at room temperature. Quantum chemical
calculations are performed to better understand the origin of the absorption features observed in experiments. Different
weight ratios of isomeric mixtures are analyzed by THZ-TDS with the help of linear regression technology. It is
concluded that THZ-TDS is able to identify the components and their relative percentage in isomeric mixtures.