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Resonance Raman spectroscopy utilizing tunable deep ultraviolet excitation for materials characterization.

机译：利用可调谐的深紫外激发进行材料的共振拉曼光谱。

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摘要

Resonance Raman spectroscopy offers some key benefits over other spectroscopy methods. In one facet, resonance Raman provides a level of specificity not present in non-resonant Raman scattering. In another facet, resonance Raman can provide increased scattering cross-sections that rival those associated with the intensities of species fluorescence. These features provide mechanisms for improved trace species detection in current Raman remote sensing applications; as well as signal level enhancement in tiny volume regimes, such as those typical in near-field optical microscopy. This dissertation presents three main thrusts that are not well documented in the previous resonance Raman studies.;We demonstrate fine resolution (approx 0:1nm) resonance tuning of the excitation wavelength corresponding to sharp absorption bands in liquid benzene and liquid toluene. The Raman spectra for these materials show an appreciable increase in scattering intensity of fundamental vibrational modes and show significant enhancements in scattering intensities for overtone and combination vibrational modes not observed with non-resonant excitation. Resonantly excited fundamental modes are observed to be enhanced by 3 to 5 orders of magnitude over non-resonant excitation; and several resonantly excited overtone modes are observed for both liquid benzene and liquid toluene.;We have observed, that for liquid benzene and liquid toluene, the maximum Raman scattering intensity is realized when the excitation wavelength corresponds to that of the vapor phase absorption maximum, not the liquid phase absorption maximum as expected. We present a simple model of the time-dependent energy accumulation in the scattering volume that suggests that the scattering medium is a highly disorganized fluid. The observed Raman scattering intensity originates from this metastable fluid observed during the liquid-vapor phase transition.;Using different concentration solutions of liquid benzene in heptane, we illustrate the influence species absorption has on the potential level of signal enhancement offered by resonance Raman scattering. In low concentration environments, resonance Raman signal levels can be 1 to 3 orders of magnitude larger than those of non-resonant Raman. As concentration increases, the signal levels of both resonant and non-resonant Raman become comparable. Using the species absorption to normalize the number of scattering molecules, the resonance enhancement is shown to be 3 to 5 orders of magnitude over the non-resonant excitation.
机译：共振拉曼光谱比其他光谱方法具有一些关键优势。在一个方面，共振拉曼提供了非共振拉曼散射所不具备的特异性水平。在另一方面，共振拉曼可以提供增加的散射截面，该截面可以与与物种荧光强度相关的散射截面相匹敌。这些功能提供了在当前拉曼遥感应用中改善痕量物种检测的机制；以及在小体积范围内的信号水平增强，例如近场光学显微镜中的典型情况。本文提出了三个主要推力，这些推力在以前的共振拉曼研究中没有得到很好的证明。我们证明了激发波长的精细分辨率（约0：1nm）共振调谐，对应于液态苯和液态甲苯中的陡峭吸收带。这些材料的拉曼光谱显示出基本振动模式的散射强度显着增加，并且对于非共振激发未观察到的泛音和组合振动模式，散射强度显着提高。观察到，与非共振激发相比，共振激发的基本模式增强了3到5个数量级。液态苯和液态甲苯都观察到了几种共振激发的泛音模式。我们已经观察到，对于液态苯和液态甲苯，当激发波长对应于气相吸收最大值时，实现了最大拉曼散射强度，不是预期的最大液相吸收。我们提出了散射体积中随时间变化的能量积累的简单模型，表明散射介质是高度杂乱的流体。观察到的拉曼散射强度源自在液-汽相变过程中观察到的亚稳态流体。通过使用庚烷中不同浓度的液态苯溶液，我们说明了物种吸收对共振拉曼散射提供的信号增强的潜在水平的影响。在低浓度环境中，共振拉曼信号电平可能比非共振拉曼信号大1至3个数量级。随着浓度的增加，共振和非共振拉曼的信号电平变得可比。使用物质吸收来归一化散射分子的数量，与非共振激发相比，共振增强显示为3到5个数量级。

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  • 作者

    Chadwick, Christopher Todd.;

  • 作者单位

    North Carolina State University.;

  • 授予单位 North Carolina State University.;
  • 学科 Physics Optics.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 159 p.
  • 总页数 159
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 光学;
  • 关键词

  • 入库时间 2022-08-17 11:38:24

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