Terahertz dynamics of complex liquids

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The commercially available conventional Terahertz time domain spectrometer (THz-TDS) is not suitable for the studies of dynamical properties of complex liquids. Therefore, the specially ordered THz-TDS was purchased from Tochigi Nikon Corporation. Since for the study of the fast relaxation process and boson peaks related to cooperative motion, the low energy excitation below 1.0 THz is very important. However, the convergent beam is used in the conventional spectrometer and the accurate determination of the phase delay of the transmitted wave is difficult. In the present investigation, the parallel beam with 5 cm diameter is used to transmit a sample as plane waves. By using this spectrometer we have systematically studied the following three kinds of materials, (l) alcohol aqueous solution, (2) cryo-protectant materials such as poly alcohols, (3) alkali borate glasses. The real and imaginary parts of complex dielectric constants have been determined from 0.1 THz to 3.0 THz. These results have been analyzed by considering non-Debye relaxation and vibrational states of medium-range order.