Terahertz Spectroscopic Investigation of Imidacloprid
YAN Zhi-gang,HOU Di-bo*,CAO Bing-hua,ZHANG Guang-xin,ZHOU Ze-kui
State Key Lab of Industrial Control Technology, Research Center for Terahertz Technology, College of Information Science and Engineering，Zhejiang University, Hangzhou 310027，China
Abstract：Terahertz radiation generated by ultra short laser pulses has a broad band width in the far-infrared range.Terahertz wave interacting with materials is a new research field.In this paper, we performed measurement of absorption coefficient and refractive index of imidacloprid in the frequency range 0.2-2.0 THz at room temperature by THz-TDS.The results indicate that imidacloprid has absorption fingerprints in this frequency range，and the absorption coefficient increases with the frequency.The average refractive index of imidacloprid is 1.65, and the refractive index of imidacloprid increases slightly with frequency. A semi-empirical theory was applied to obtain the structure and vibrational frequencies of the imidacloprid molecules in THz region.The calculated results agree well with the experimental data.The absorption features are caused by the collective vibrational and torsional modes, and different absorption peaks correspond to different vibrational modes.The comparison between experimental and theoretical study shows that far-infrared absorption features are highly sensitive to the structure and spatial arrangement of the molecules.THz-TDS is a potential tool to understand the collective vibrational modes and conformational structures of bio-molecules.
[1] Ferguson B, Zhang X C.Nature materials, 2002, 1(1)：26. [2] Boyd J E, Briskman A, Colin V L, et al.Phys.Rev.Lett., 2001, 87：147401. [3] Huber R, Tauser F, Brodschelm A, et al.Nature, 2001, 414：286. [4] Walther M, Fischer B, Schall M, et al.Chem.Phys.Lett., 2000, 332：389. [5] HU Ying, ZHANG Cun-lin, SHEN Jing-ling，et al(胡 颖，张存林，沈京玲，等).Acta Phys.Sin.(物理学报)，2004, 53(6)：1772. [6] LIU Rui, GU Chun-ming, HE Li-rong，et al(刘 锐，顾春明，贺莉蓉，等).Acta Phys.Sin.(物理学报)，2004, 53(4)：1217. [7] Petruck C R，Jimenez R, Guo T，et al.Nature，1999，389：310. [8] Zhuang W, Feng Y，Prohofsky E W.Phys.Rev.A，1990，41：7033. [9] Brucherseifer M, Nagel M, Haring Bolivar P，et al.Appl.Phys.Lett., 2000, 77：4049. [10] MA Guo-xin, WANG Cheng-long, FAN Duo-wang，et al(马国欣, 王成龙, 范多旺, 等).Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2006, 26(3)：434. [11] TANG Fu-bin, LIU Guang-ming, LUO Feng-jian, et al(汤富彬， 刘光明，罗逢健，等).Chinese Journal of Pesticide Science(农药)，2004, 43(12)：561. [12] Derney T D, Baraniu K, Mittleman D M.Journal of the Optical Society of America A：Optics, Image Science, and Vision, 2001, 18(7)：1562. [13] Duvillaret L, Garet F, Coutaz J L.Applied Optics, 1999, 38(2)：409. [14] WANG Wei-ning, LI Yuan-bo, YUE Wei-wei(王卫宁，李元波，岳伟伟).Acta Phys.Sin.(物理学报), 2007, 56(2)：781.
