The Measurement Of The Terahertz Spectrum Of Water

Water is a kind of ubiquitous liquid on earth, which has some peculiar characteristics in physics and thermodynamics, though H2O molecule is very simple. A many-body system is formed by the interaction between water molecule and hydrogen-bond. Terahertz wave would be greatly absorbed by this system, so it will help us study the characteristics of water to measure the spectrum of water in terahertz (THz) domain. THz time-domain spectroscopy (THz-TDS) has been playing a more and more important role in many research areas due to its particular advantages such as broadband detection, high signal-to-noise ratio, high time resolution and phase coherent detection. We obtain the absorption coefficient and refraction index of water using THz-TDS technology, and the result will be valuable to study on the structural and thermodynamic properties of water.The most popular method of terahertz generation and detection is summarized, and THz time-domain spectroscopy system is described detailedly as well as our experiment scheme. Besides, we obtain the spectrum of water in terahertz domain at different temperatures. We propose a method to measure the thickness of water membrane using the terahertz transmission wave form through ice, which solves the difficult problem in the transmission spectroscopy. The result, which is in good agreement with references, shows that terahertz wave is absorbed in all THz range, and has no resonant absorption peak except the one nearby 60 cm-1. Besides, we obtain the terahertz spectrum of ice and mixture of water and ice.