Abstract: The terahertz (THz) spectra of butyl hydroxy anisole (BHA) and its mixtures were measured in the frequency range of 0.2 - 2.6 THz by the THz time-domain spectroscopy. The results show that there are three distinctive absorption peaks in this frequency range, which were found at 0.64 THz, 1.14 THz and 1.81 THz. It can be used to identify this substance. In addition, the terahertz spectra of BHA mixture were analyzed by the least squares method. The results show that the correlation between terahertz absorption coefficient and the mass fraction of BHA is larger than 0.98. Finally, the numerical calculations based on the density functional theory are carried out for the single-molecule butyl hydroxy anisole.The results show that the terahertz absorption peaks have relationship with molecular conformation and molecular motion inside.

Key words: Spectroscopy；Absorption spectra；Least Squares Method；Density Functional Theory；Quantitative Analysis