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首页> 外文学位 >Terahertz frequency analysis of gaseous and solid samples using terahertz time-domain spectroscopy.
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Terahertz frequency analysis of gaseous and solid samples using terahertz time-domain spectroscopy.

机译：使用太赫兹时域光谱仪对气态和固态样品进行太赫兹频率分析。

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摘要

Developments in semiconductor and laser technologies have facilitated development of terahertz (THz)-frequency (∼2-200 cm -1) technologies. Results published in the literature as far back as the early 20th century demonstrate the utility of this frequency range for myriad applications, but the improved performance of modern THz technologies has renewed interest in THz-frequency analysis. Material presented in this dissertation focuses on three applications of terahertz time-domain spectroscopy (THz-TDS): quantitation of gas-phase molecular species, analysis of polymeric materials, and investigation of dental tissue/composite structures.;Gas phase species were quantified individually at concentrations ranging from several parts per million to several parts per thousand using various chemometric methods. Quantitative model robustness was evaluated by comparison of model precision, and partial least-squares (PLS) regressions provided the greatest precision. Species were quantified in mixtures using PLS with errors of prediction below the permissible exposure limits (PELs) set by the Occupational Safety and Health Administration. The effect of spectral broadening as a result of overall sample pressure was investigated, and species were analyzed in mixtures at various overall pressures. Errors of prediction were again near or below the PELs, demonstrating the utility of this method for atmospheric analysis. Chemical selectivity available in THz spectral features was evaluated and compared to selectivity available in infrared frequencies.;Spectral parameters measured in the THz frequency range also provide insight into structural properties of polymeric materials. In some cases, spectral peaks may be used to identify the temperature at which phase changes occur within these materials. THz refractive index spectra were found to be a sensitive and non-destructive tool for identification of phase transition temperatures.;The time-resolved measurement of THz-TDS makes it particularly useful for rapid, non-destructive analysis of layered structures. Ordinarily, the strength of bonds between dental tissues and composite materials are evaluated in the laboratory using destructive failure analyses. Transparency of dental tissues and composite materials used for restorative procedures to THz pulses allows investigation of interfaces between these materials. Refractive index spectra indicate locations in which delamination has occurred between bonded layers. These results provide an overview of unique capabilities of the THz-TDS method in real-life spectral analyses.
机译：半导体和激光技术的发展促进了太赫兹（THz）频率（〜2-200 cm -1）技术的发展。早在20世纪初期，发表在文献中的结果就证明了该频率范围在众多应用中的实用性，但是现代THz技术的性能提高引起了人们对THz频率分析的兴趣。本论文介绍的材料主要针对太赫兹时域光谱（THz-TDS）的三种应用：气相分子种类的定量，聚合物材料的分析以及牙科组织/复合结构的研究。使用各种化学计量方法的浓度范围从百万分之几到千分之几。通过比较模型精度来评估定量模型的鲁棒性，偏最小二乘（PLS）回归提供了最大的精度。使用PLS对混合物中的物种进行定量，其预测误差低于美国职业安全与健康管理局（USHA）设定的允许暴露极限（PEL）。研究了由于总样品压力导致的光谱展宽的影响，并在各种总压力下分析了混合物中的物质。预测误差再次接近或低于PEL，表明该方法可用于大气分析。评估了太赫兹光谱特征中可用的化学选择性，并将其与红外频率中的选择性进行了比较。在太赫兹频率范围内测量的光谱参数还提供了对聚合物材料结构特性的了解。在某些情况下，光谱峰可用于识别这些材料中发生相变的温度。太赫兹折射率光谱被发现是用于识别相变温度的灵敏且无损的工具。THz-TDS的时间分辨测量使其特别适用于层状结构的快速，无损分析。通常，在实验室中使用破坏性破坏分析来评估牙组织与复合材料之间的粘结强度。用于THz脉冲修复过程的牙组织和复合材料的透明度允许研究这些材料之间的界面。折射率光谱表示在粘合层之间发生分层的位置。这些结果概述了THz-TDS方法在实际频谱分析中的独特功能。

著录项

  • 作者

    Smith, Ryan Michael.;

  • 作者单位

    The University of Iowa.;

  • 授予单位 The University of Iowa.;
  • 学科 Chemistry Analytical.
  • 学位 Ph.D.
  • 年度 2012
  • 页码 466 p.
  • 总页数 466
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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