Angle-dependent terahertz time-domain spectroscopy of amino acid single crystals

The measurement of absorption spectra using angle-dependent terahertz (THz) time-domain spectroscopy for amino acid single crystals of L-cysteine and L-histidine is reported for the first time. Linearly polarized THz radiation enables us to observe angle-dependent far-infrared absorption spectra of amino acid single crystals and determine the direction of the oscillating dipole of the molecules in the 20-100 cm -1 range. By comparing the THz spectra of a single crystal and powder, we found that there was a clear hydrogen-bond peak in the crystal spectrum as a result of the larger hydrogen-bond network. The low-temperature THz spectra of amino acid microcrystals showed more intermolecular vibrational modes than those measured at room temperature. An ab initio frequency calculation of a single amino acid molecule was used to predict the intramolecular vibrational modes. The validity of the calculation models was confirmed by comparing the results with experimentally obtained data in the Raman spectral region

Broadband dielectric spectroscopy of glucose aqueous solution: Analysis of the hydration state and the hydrogen bond network.

Recent studies of saccharides' peculiar anti-freezing and anti-dehydration properties point to a close association with their strong hydration capability and destructuring effect on the hydrogen bond (HB) network of bulk water. The underlying mechanisms are, however, not well understood. In this respect, examination of the complex dielectric constants of saccharide aqueous solutions, especially over a broadband frequency region, should provide interesting insights into these properties, since the dielectric responses reflect corresponding dynamics over the time scales measured. In order to do this, the complex dielectric constants of glucose solutions between 0.5 GHz and 12 THz (from the microwave to the far-infrared region) were measured. We then performed analysis procedures on this broadband spectrum by decomposing it into four Debye and two Lorentz functions, with particular attention being paid to the β relaxation (glucose tumbling), δ relaxation (rotational polarization of the hydrated water), slow relaxation (reorientation of the HB network water), fast relaxation (rotation of the non-HB water), and intermolecular stretching vibration (hindered translation of water). On the basis of this analysis, we revealed that the hydrated water surrounding the glucose molecules exhibits a mono-modal relaxational dispersion with 2-3 times slower relaxation times than unperturbed bulk water and with a hydration number of around 20. Furthermore, other species of water with distorted tetrahedral HB water structures, as well as increases in the relative proportion of non-HB water molecules which have a faster relaxation time and are not a part of the surrounding bulk water HB network, was found in the vicinity of the glucose molecules. These clearly point to the HB destructuring effect of saccharide solutes in aqueous solution. The results, as a whole, provide a detailed picture of glucose-water and water-water interactions in the vicinity of the glucose molecules at various time scales from sub-picosecond to hundreds of picoseconds

Surface Phenomena of Semiconductor Materials : An Investigation using Raman Microscopy

報告番号: 甲11520 ; 学位授与年月日: 1995-09-29 ; 学位の種別: 課程博士 ; 学位の種類: 博士(工学) ; 学位記番号: 博工第3524号 ; 研究科・専攻: 工学系研究科応用化学専

顕微ラマン分光法を用いた半導体材料の界面現象に関する研究

University of Tokyo (東京大学

Continuous wave terahertz spectroscopy system designed for medical field

We have constructed a continuous wave (CW) terahertz spectroscopy system using photonic integration-compatible technology. This system is intended for use in the medical field as a miniaturized terahertz spectroscopy system, in contrast to the conventional pulsed wave method. This system can simultaneously measure the absorption and phase (dielectric constant) responses of a sample, and it exhibits a dynamic range of at least 75 dB at under 1 THz. In addition, we used the CW spectroscopy system to identify a new type of complex molecule crystal (cocrystal) formed from a molecule of a pharmaceutical drug and various coformers. Cocrystals have been developed for use in the pharmaceutical manufacturing field to improve the solubility and absorbability of medicines. By fixing the measurement frequency at the absorption peak of intermolecular interactions of those crystals, we obtained a two-dimensional distribution of cocrystals within a test tablet.11Nscopu