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21 世紀 COE 外国旅費補助・成果報告

21 世紀 COE 外国旅費補助・成果報告. 物理学第一教室　光物性研究室　 D2 　矢田祐之. 2007 年 10 月 18 日（木）理学部４号館（宇宙物理教室）講義室 (414 号室）. 会議の概要. 名称 : The International Conference on I nfrared, M illi m eter, and T era h ert z W aves (IRMMW-THz) 場所 : Cardiff, UK 期間 : 2007/9/3~9/7 規模： 18 カ国から 430 人以上が参加 4 つのパラレルセッション

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21 世紀 COE 外国旅費補助・成果報告

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  1. 21世紀COE外国旅費補助・成果報告 物理学第一教室　光物性研究室　D2 　矢田祐之 2007年 10 月 18 日（木）理学部４号館（宇宙物理教室）講義室(414号室）

  2. 会議の概要 • 名称:The International Conference on Infrared, Millimeter, and TerahertzWaves (IRMMW-THz) • 場所 :Cardiff, UK • 期間 : 2007/9/3~9/7 • 規模：18カ国から430人以上が参加 • 4つのパラレルセッション • 概要：赤外波、ミリ波、テラヘルツ波の 発生検出技術およびその応用を議論 • （例 セキュリティ、天文、医療、通信、分光分析・・・） カーディフ：ウェールズ地方の首都 人口：30万人　産業革命以降、カーディフ港からの石炭の積み出しで、飛躍的に発展した。

  3. 分野の概要 分子間振動 分子回転 分子内振動 電子遷移 X線回折 配向緩和 プラズマ振動 300MHz 1m 3GHz 100mm 30GHz 10mm 300GHz 1m 3THz 100mm 30THz 10mm 300THz 1mm 3PHz 100nm 10nm 1nm 電波 ミリ（マイクロ）波 遠赤外 中赤外 近赤外 紫外 X線 g線 可視光 THz領域 応用：Ｘ線と補完的なイメージング光源 本研究の対象は水の分光

  4. テラヘルツ時間領域分光法 半導体素子 (光伝導アンテナ) 光サンプリング検出 (電気光学効果) サンプル 超短パルスファイバーレーザー (50MHz, 780nm, 20mW, 90fs) THz Time-Domain Spectroscopy (THz-TDS) =実時間電場波形を検出 →複素誘電率を測定できる。

  5. WedB3-3 Picosecond Dynamics of Water and Heavy Water Investigated by Using Terahertz Time-Domain Attenuated Total Reflection Spectroscopy Hiroyuki YADA, Masaya NAGAI, and Koichiro TANAKA Department of Physics, Kyoto University, Japan This work is supported by Center for Diversity and Universality in Physics (CDUP). IRMMW-THz 2007, Cardiff (September 3rd-7th )

  6. Background of this study Picosecond dynamics of water gives a basis for understanding the biochemical reaction in water, such as hydration dynamics(->WedB3-1). Intermolecular stretching vibration mode and libration mode 5 THz, 14 THz (Raman and far-infrared spectroscopy) Water dynamics in ps timescale Collective relaxation mode 20 GHz (Dielectric measurement) Individual mode ? 1.5 THz THz component(THz TDS) Forming and breaking of hydrogen bonding Picosecond timescale (MD) Collective motions of dipole moments due to the fluctuation of hydrogen bonding network

  7. Amplitude Dispersion of vibration mode Recent research on THz component • Rønne et al. made THz spectroscopy (~2.0 THz) • and found that THz component is Debye relaxation mode. [1] C. Rønne, et al., J. Chem. Phys. 107, 5319 (1997). [2] C. Rønne, P. -O. Åstrand and S. R. Keiding, Phys. Rev. Lett. 82, 2888 (1999).

  8. Purpose of this study To reveal the physical origin of the THz component • Accurate measurements of temperature dependence of complex dielectric constants of water and heavy water have been made in wider frequency region [ 0.2 ~ 3.5 THz]. • Analysis taking into account vibration modes has been made to estimate the contribution of vibration mode.

  9. Reflection-type measurement near the critical angle • more sensitive than normal reflection (->WedB3-1) • Reference is easily measured by removing water. THz Time-Domain Attenuated Total Reflection Spectroscopy A. ATR C. Normal [1] N. J. Harrick, “Internal Reflection Spectroscopy”, Interscience, (1967). [2] H. Hirori et al., Jpn. J. Appl. Phys. 43, L1287-L1289 (2004). [3] H. Hirori et al., OPTICS EXPRESS 13, 10801 (2005). [4] M. Nagai et al., J. Int. Infrared Millimeter Waves 27, 505 (2006).

  10. Temperature dependence • Small increase in real part • Significant increase in Imaginary part • -> GHz Debye mode Temperature dependence of complex dielectric constants of water • Room temperature • Rapid Increase in Im() in low frequency • -> GHz Debye mode • Gradual increase in Im() in high frequency • -> Vibration in 5 THz

  11. Temperature dependence of complex dielectric constants of heavy water • The temperature dependence is almost the same with water. • ->GHz Debye mode

  12. Temperature dependence of the GHz Debye mode water [1] R. J. Speedy and C. A. Angell, J. Chem. Phys. 65, 851 (1976). [2] P. S. Yastremskii, J. Structural Chemistry 29, 483 (1988). [3] C. Rønne, et al., Phys. Rev. Lett. 82, 288 (1999). [4] G. A. Vidulich, D. F. Evans, and R. L. Key, J. Phys. Chem. 71, 656 (1985).

  13. Water H2O 20 ºC 10 e i 1 ? 0.1 ei Collective Relaxation mode 20 GHz Intermolecular stretching vibration mode 5.4 THz 0.01 THz component 1.5 THz Libration mode 14 THz 0.001 100 0.0001 0.001 0.01 0.1 10 1 Decomposition into 4 components Frequency [THz] [1] M. N. Afsar et al., J. Opt. Soc. Am., 67, 116 (1977). [2] U. Kaatze, J. Chem. Eng. Data 34, 371 (1989). [3] J. M. Alison et al., Meas. Sci. Tech. 2, 975 (1991). [4] A. N. Rusk et al., J. Opt. Soc. Am. 61, 895 (1971).

  14. THz component at room temperature We connect our data to far-infrared results [1]. C. Rønne, et al., J. Mol. Liq. 101, 199 (2002). Our results The relaxation time is longer both in H2O and D2O. [1] M. N. Afsar and J. B. Hasted, L. J. Opt. Soc. Am., 67, 116 (1977) .

  15. Decomposition into 4 components We reduce the fitting parameters for stretching vibration and libration mode. Temperature dependences of amplitudes are determined so that integral of the imaginary part can be constant. The values at room temperature are used. Temperature dependence of resonant frequencies are determined by referring to far-infrared result [1]. [1] H. R. Zelsmann, J. Mol. Structure 350, 95 (1995).

  16. Temperature dependence of the THz component • The amplitude is almost constant. • Relaxation times are longer and almost constant. • Isotope shift is observed. [1] C. Rønne, et al., J. Chem. Phys. 107, 5319 (1997).

  17. Discussion 1 • Our findings • Little temperature dependence of relaxation time of THz component • Isotope shift of the relaxation time of THz component • Liquid water • Collective mode (Large) • THz Debye mode (small) • Supercritical water • The temperature is high. • The density is low. • Collective mode • THz Debye mode (remain) individual mode ? P If it is individual mode. 491 K, 218 atm. This is observed in GHz dielectric measurement [1]. T [1] K. Okada, M. Yao, Y. Himejima, H. Kohno, and Y. Kajihara, J. Chem. Phys. 110, 3026 (1998).

  18. Collective mode Individual mode miss Collision model Hard sphere Hit Discussion 2 • 10 % of hydrogen bondings are broken. (Thermal experiment) • Forming and breaking of hydrogen bondings ~ 0.3 ps (MD) [1] K. Okada, et al., J. Chem. Phys. 110, 3026 (1999). [2] A Luzar and D. Chandler, Nature 379, 55 (1996). THz component is Individual mode.

  19. Summary • We have determined temperature dependence of dielectric constants of water and heavy water in the range from 0.2 THz to 3.5 THz, -6 ºC to 91 ºC by THz-TD-ATR spectroscopy. • We have decomposed the dielectric constants into four components,GHz Debye mode, THz Debye mode, stretching vibration mode, and libration mode. • In terms of the temperature dependence and isotope shift,THz component has been assigned to individual relaxation mode. 成果：研究発表および共同研究（ATR法の技術協力）の議論ができ、意義深い国際会議であった。

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