Discrimination of Inflammable Liquids by Two-Dimensional Mapping of Complex Refractive Indices in the Terahertz Range

Terahertz time-domain spectroscopy has been applied to the discrimination of inflammable liquids. Indices of refraction and absorption coefficients of some inflammable liquids reflect those of their ingredients, such as alkanes and aromatic hydrocarbons. The inflammable liquids can be distinguished from each other by plotting their values on a two-dimensional map, in which two axes are the index of refraction and absorption coefficient at 30 cm-1. We also plotted the values of the inflammable liquids on a two-dimensional map, in which two axes are the amplitude transmittance and optical delay at the peak of the terahertz waveform. It demonstrates that the discrimination of inflammable liquids is possible without Fourier transformation of the terahertz waveform.