Terahertz spectrum of ellagic acid

The absorption and refractive index of ellagic acid in the range of 0.2-2.4 THz have been measured by THz-TDS. It is found that the ellagic acid has the fingerprint absorption in this frequency region. The vibration absorption spectrum of the single molecule of ellagic acid between 0.2 and 2.4 THz is simulated based on the Density Functional Theory (DFT). THz absorption at low frequencies is attributed to the vibration absorption of water of crystallization. The results presented in this paper will be helpful for the inspection of medicine and food.