Keywords: 
• L-天冬酰胺 /
• 太赫兹时域光谱 /
• 特征吸收 /
• 结晶水

Abstract: Low-frequency collective vibrational modes of biomolecules which often lie in terahertz (THz) band, make the ter-ahertz time-domain spectroscopy (THz-TDS) an important technique for molecular identification and medicine quality inspection. Distinctive THz spectra between L-asparagine and its monohydrate were observed and the dehydration pro-cess of L-asparagine monohydrate was tracked by THz-TDS. Experiments indicate that THz wave is sensitive to phase transitions in crystals, dehydration process, and weak molecular interactions. Multi-techniques including differential scanning calorimetry and thermogravimetry, Fourier transform infrared spectroscopy, and powder X-ray diffraction are performed to investigate the thermodynamic properties, intermolecular and intramolecular vibrations, and molecular packing patterns of L-asparagine and its monohydrate. These measurements support the reliability of THz spectroscopy. To simulate and analyse the vibration modes of L-asparagine monohydrate, density functional theory calculations are per-formed using a Perdew Burke and Ernzerhof generalized gradient approach;the results agree well with the experimental observations.