Measurement of water absorption coefficient using terahertz time-domain spectroscopy

Terahertz time-domain spectroscopy (TDS) is advantageous to analyze the absorption spectrum of water since the terahertz electromagnetic waves are absorbed very well. The measurement confirms the absorption coefficient of the pure water increases with the frequency from 0.04 THz to 0.8 THz. Moreover, the absorption increases with an increment of the concentration of Na⁺ ion in the pure water especially in the low frequency region.