3种苯基脲类除草剂的THz光谱特性研究

利用太赫兹时域光谱(THz-TDS)技术对3种苯基脲类除草剂,敌草隆、伏草隆、绿麦隆的标准品分别进行光学参数的测试,获得样品在有效THz波段范围的折射率谱和吸收谱.实验结果发现,三种样品的吸收谱均有明显的特征吸收峰,且它们之间存在很大差异,平均折射率分别为1.593、1.474、1.504.利用Gaussian03的B3LYP函数在6-311G(d)基组水平上计算其单分子的振动频率,模拟结果与实验数据存在一定差异,说明单分子模拟存在局限性.利用DMol3程序的BP函数,在DNP基组水平上进行晶体振动频率模拟,模拟结果与实验数据一致性较好.通过实验和理论分析,THz-TDS技术可作为鉴别这三种除草剂的一种有效手段.     

太赫兹技术在水泥基材料研究中的应用

本文介绍了太赫兹波的特性以及太赫兹技术的工作原理及其应用,重点介绍了太赫兹时域光谱技术和太赫兹成像技术在水泥水化过程、水泥基材料的微观结构检测和水泥基材料耐久性能三方面的研究进展.利用太赫兹光谱技术可跟踪硅酸三钙、硅酸二钙以及主要水化产物水化硅酸钙、氢氧化钙在水化过程中的变化情况;利用水分对太赫兹波强烈吸收的特性,能够...     

磁控溅射超薄金属膜在太赫兹波段的光学特性

采用THz时域光谱测试技术，对Fe扣Co的超薄金属膜在0.2～2，5THz波段的吸收特性、透射特性以及折射率进行了研究。在室温并去除水份影响的氮气环境中，获得了不同种类扣不同厚度的薄金属膜在太赫兹波段的时域谱．利用Origin7．0扣Matlab7，0软件处理得到这些金属薄膜对太赫兹波的透射率，吸收系数扣折射率．对比发现金属超薄膜在太赫兹波段的光学特性随薄膜厚度以及太赫兹波频率的变化有很大的改变，也就是具有明显的尺寸效应．同时根据所得到的折射率开口吸收系数还可以理论上计算出不同种类与厚度的超薄金属膜在太赫兹波段的复介电函数．     

应用太赫兹技术对云冈石窟不同岩石样品的分析

利用可实现无损检测的太赫兹时域透射光谱系统,测量由云冈石窟第四窟所采集的风化石雕和附近山体深部未被风化的岩石样品的时域谱.用Origin和Matlab软件处理数据得到样品的吸收谱和折射谱.通过比较分析得出,在低频区两组样品的吸收系数差别不大而且吸收都很弱,在高频区未被风化岩石样品的吸收系数大于已风化石雕样品.在整个波段...     

等离子体中太赫兹波传输及成像探测特性研究

本文根据散射矩阵方法模拟等离子体并建立了非均匀等离子体理论模型,并在此基础上计算了0.1 THz^10 THz频段的全波段太赫兹波在其中的传输特性。根据介质阻挡放电原理在实验室环境下搭建等离子体射流产生装置并产生非均匀等离子体,进行了太赫兹时域光谱(THz-TDS)以及宽带太赫兹源在等离子体中的透射光谱测量以及太赫兹波对等离子体遮挡下目标物的反射成像的试验。理论和实验结果均表明,较高频太赫兹波在等离子体中有良好的穿透性,这为太赫兹波在黑障区的通信以及雷达探测应用打下研究基础。     

太赫兹量子级联激光器功率达到1W

正近日国外网媒报道,奥地利维也纳技术大学的一组研究人员制造出一种新型量子级联激光器,成功输出了1W的太赫兹辐射,打破了此前由美国麻省理工学院所保持的0.25W的世界纪录,成为目前世界上功率最大的太赫兹量子级联激光器。太赫兹射线是波长介于微波与红外之间的一种电磁辐射,由于物质的太赫兹光谱(包括透射谱和反射谱)包含非常丰富的物理和化学信息,太赫兹技术被认为会对通信、遥感、天文、反恐、医学成像以及生     

基于太赫兹频域光谱技术测定吡虫啉的浓度

目的:测定吡虫啉的特征吸收峰以及检测不同浓度的吡虫啉。方法:采用太赫兹频域光谱测定吡虫啉的特征吸收峰。采用太赫兹频域光谱技术和偏最小二乘回归算法检测吡虫啉的浓度。结果:吡虫啉在0.88 THz处存在特征吸收峰,吸收峰的吸光度随着浓度的增加而增加。不同浓度吡虫啉的偏最小二乘回归模型具有较高的相关系数、较低的校准均方根误差、较低的交叉验证均方根误差和较低的预测均方根误差。结论:太赫兹频域光谱结合化学计量学方法可以检测吡虫啉的浓度。     

SiC和Si_3N_4粉体的太赫兹时域光谱研究

采用太赫兹时域光谱装置测试SiC和Si3N4粉体在0.4～2.4 THz的透射光谱,研究SiC和Si3N4粉体对太赫兹波的吸收性能与其电导率的关系,分析SiC和Si3N4粉体对太赫兹波的散射特性。结果表明,SiC是一种半导体材料,其内部含有较多可以自由移动的载流子,对太赫兹波的吸收较强;Si3N4是绝缘性很好的材料,对太赫兹波的吸收很小;SiC和Si3N4粉体对太赫兹波的散射作用属于瑞利散射,但是测试波长比粉体粒径大得多,散射效果不明显。     

太赫兹技术在医学科学中的应用及研究进展

近年来太赫兹光(0.1 THz~10 THz)因其良好的探测能力和非电离特性受到研究者们的关注。根据不同的检测方式和信号处理方法,可分为太赫兹成像技术和太赫兹光谱技术两大类。太赫兹技术在医学科学中发展迅速,其中生物大分子检测和组织成像令人印象深刻。水含量和结构差异是太赫兹成像技术的理论基础,据此可对生物组织进行检测识别。不同的生物组织具有不同的太赫兹特征谱,太赫兹光谱技术通过检测吸收系数、折射系数和反射系数来识别不同的生物分子、细胞或组织。实时、无标记的检测方式有望在临床实践中发挥重要作用,但仍需克服生物安全性不明等困难。综述介绍了太赫兹技术在医学科学中的应用及研究进展,同时探讨了太赫兹技术目前需要克服的难题和潜在的生物安全性问题。

     

膜厚对导电氧化锌宽带抗反射涂层的太赫兹传输影响

利用直流磁控溅射方法,在石英基底上制备了可用于太赫兹电磁波频率范围内的宽带抗反射涂层的掺铝氧化锌导电薄膜。在太赫兹时域光谱频率0.1~1.0THz范围内研究不同厚度的氧化锌薄膜的介电响应,得到了与频率相关的电导率、吸收和薄膜折射率,着重研究了膜厚对太赫兹波传输特性的调制作用。实验结果很好地符合了经典的Drude模型,表明可以通过控制氧化锌薄膜的厚度来改变太赫兹波的传输特性,并且导电氧化锌薄膜能够作为太赫兹频段范围的宽带抗反射涂层应用于衬底和光学器件上。     

Investigation of THz birefringence measurement and calculation in Al₂O₃ and LiNbO₃

Based on the polarization-sensitive terahertz time-domain spectroscopy, we measured the birefringence for Al?O? and LiNbO? single crystals, which correspond to trigonal structures that have an uniaxial birefringence, in the THz frequency range of 0.25 to 1.4 THz. For more comprehensive understanding of the THz birefringence, the measured birefringence is compared with the results of ab initio calculations. The measured birefringence shows good agreement with the calculated value.     

Identification and quantification of polymorphism in the pharmaceutical compound diclofenac acid by terahertz spectroscopy and solid-state density functional theory

Polymorph detection and quantification in crystalline materials is a principle interest of the pharmaceutical industry. Terahertz (THz) spectroscopy can be used for such analytical applications since this technique is sensitive to the intermolecular interactions of molecules in the solid state. Understanding the fundamental nature of the lattice vibrational motions leading to absorptions in THz spectra is challenging, but may be achieved through computational approaches. In this study, the THz spectra of two diclofenac acid polymorphs were obtained by THz spectroscopy, and the vibrational characters of the observed absorptions were analyzed using solid-state density functional theory (DFT). The results demonstrate the quantitative capacity of THz spectroscopy and the reliability and utility of solid-state DFT in the calculation of low-frequency vibrational motions.     

太赫兹时域谱的动物皮革光学特性

利用THz时域谱技术对猪皮、牛皮、羊皮在0.2~1.7 THz波段的吸收特性进行了研究.精确测量其折射率、吸收系数等光学参数用于对皮革成分分析以及质量评价,获得了三种皮革样品的吸收峰位置.该研究成果表明,THz-TDS技术可以用于对皮革成分快速检测.     

Terahertz wave propagation in one-dimensional periodic dielectrics

We demonstrate the temporal evolution of terahertz (THz) wave propagation in one-dimensional periodic dielectrics. Distributed Bragg reflectors and a resonant cavity are investigated: The structures involve air gaps interleaved between polymer films. Transmitted and reflected broadband THz waves are measured by means of THz time-domain spectroscopy. The experimental results agree well with transfer matrix calculations.     

Far-infrared spectroscopic characterization of explosives for security applications using broadband terahertz time-domain spectroscopy

Broadband terahertz time-domain spectroscopy (THz-TDS) has been used to measure the far-infrared (FIR) vibrational spectra of several commonly used pure explosives, including 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), 1,3-dinitrato-2,2-bis(nitratomethyl)propane (PETN), and two types of plastic explosive, SEMTEX and SX2. A number of distinct absorption peaks, originating from FIR-active vibrational modes of these polycrystalline energetic materials, were observed in the frequency range 0.3-7.5 THz (10-250 cm(-1)). In addition, the temperature-dependent FIR vibrational spectra of PETN were measured between 4 K and 296 K with several well-resolved absorption peaks observed across this temperature range. We find that as the temperature is reduced, the observed absorption peaks resolve into narrower features and shift towards higher frequencies. The temperature dependence of the spectra is explained in terms of the anharmonicity of the vibrational potentials of crystalline compounds, and an empirical fit is given to describe the peak shift with temperature.     

Nondestructive defect identification with terahertz time-of-flight tomography

We demonstrate the application of terahertz (THz) time-of-flight tomographic imaging to identify the distribution of defects in foam materials. Based on THz time-domain spectroscopy technology, THz imaging probes targets with picosecond pulses of broad-band radiation in the frequency range from 100 GHz to 3 THz. The reflected THz wave from the target is measured using electrooptic sampling, which provides two-dimensional images with phase and amplitude information, as well as the spectroscopic properties of the object. The depth information is recorded in the THz time-domain waveform. Several reconstruction models are developed for tomographic imaging of defects inside foam. Foam insulation of space shuttle fuel tanks, with prebuilt defects, are investigated with THz tomographic imaging. Most prebuilt defects are pinpointed and models used to identify different kinds of defects are discussed.     

Terahertz time-domain spectroscopy studies of the optical constants of the nematic liquid crystal 5CB

The optical constants of a nematic liquid crystal, 4'-n-pentyl-4-cyanobiphenyl (5CB), in the frequency range 0.3-1.4 THz were determined by terahertz (THz) time-domain spectroscopy. The real parts of the extraordinary refractive index n(e) and the ordinary refractive index n(o) of 5CB varied from 1.74 to 2.04 and from 1.59 to 1.83, respectively. Liquid-crystal 5CB exhibits a relatively small absorption loss in this frequency range. The birefringence of 5CB was found to be as large as 0.21. The experimental results indicate that liquid crystal 5CB is potentially useful for device applications in the THz frequency range.     

Optical-induced absorption tunability of Barium Strontium Titanate film

The absorption tunability of 100 nm thickness of ferroelectric Barium Strontium Titanate (Ba_0.5Sr_0.5TiO₃) thin films with different densities of pumped optical field is measured by terahertz time-domain spectroscopy in the range of 0.2 THz – 1.2 THz at 19 °C. Experimental results show that the absorption coefficient of BST film is approximately at 5000 cm⁻¹–20000 cm⁻¹ in the range of 0.2 THz – 1.2 THz and the absorption coefficient reached up to 16% when we applied the optical field up to 600 mW. The theoretical calculations reveal that increasing photoexcitation fluences is responsible for the increasing of transmission change in the conduction current density cause the absorption coefficient varied.     

Characterization of original and expanded leaf-roots of tobacco by terahertz spectroscopy and X-ray microanalysis

Expanded leaf-roots of tobacco are used as fillers into cigarette products to reduce cost and contents of tar and nicotine and improve quality. To study the difference between expanded and original leaf-roots of tobacco, terahertz (THz) time-domain spectroscopy was used to detect the absorption spectra in the frequency range from 0.2 to 1.5 THz. Significant difference in terahertz absorption was observed in original and expanded leaf-roots. To understand the origin, scanning electron microscope was employed for microanalysis, revealing the difference in element compositions and surface appearances between original and expended leaf-roots. Non-polar and low-polar components of leaf-roots were largely lost after dissolving into liquid CO₂ during expansion, accounting for the difference in THz absorption spectroscopy.     

高效液相色谱-紫外检测禽蛋及其制品中三聚氰胺

建立了用高效液相色谱-紫外检测法检测禽蛋及其制品中三聚氰胺的方法。采用乙腈作为样品中蛋白质的沉淀剂和三聚氰胺提取剂,流动相为0.05mol/L(pH=3.00)的磷酸二氢钾乙腈缓冲溶液,检测波长为240nm,流速为1.50mL/min,SCX(Luna 5u SCX250×4.6mm)色谱柱进行分离,HPLC-UV检测,外标法定量。结果表明,该方法简便快捷,线性范围0.20～10.00mg/L,回收率在99.8%-109.4%,线性关系良好R2=1.000,可广泛应用于禽蛋及其制品中三聚氰胺的检测。