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首页> 外文学位 >Gas phase cluster studies using a desk-top size soft x-ray laser for single photon ionization.
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Gas phase cluster studies using a desk-top size soft x-ray laser for single photon ionization.

机译：气相簇研究使用台式尺寸的软X射线激光进行单光子电离。

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摘要

This dissertation reports the study of the structure and reactivity of clusters using a new mass spectrometry approach in which the ionization is produced by high energy photons generated by a desk-top size soft x-ray (SXR) laser. The work was motivated by the importance that catalytic processes have in enhancing the rate of gas phase chemical reactions such as the manufacture of hydrocarbons, polymers, drugs, sulfuric acid, fertilizers, pesticides, etc., many forms of pollution control, development of robust mirror coatings for extreme ultraviolet (EUV) lithography, and hydrogen storage for clean energy applications. Extensive mass spectrometry studies have shown that gas phase nanoclusters are effective model systems to study surface reactions in the bulk phase. However, the use of multi-photon ionization or electron impact ionization sources results in cluster fragmentation, limiting the information gained about the neutral cluster parent. Our approach uses the 26.5 eV photons of a compact capillary discharge driven laser to ionize clusters by single photon events, avoiding the cluster fragmentation associated with multi-photon ionization. The high photon energy also allows the detection of neutral clusters and small molecule reaction products with high ionization energies.;Experiments were conducted for several types of clusters including van der Waals clusters, metal oxides, and metal oxide reactions. Density Functional Theory (DFT) calculations were employed to elucidate cluster geometries, properties, and reaction mechanisms. For hydrogen/van der Waals clusters, the unimolecular dissociation rate constants for reactions involving loss of one neutral molecule were calculated and neutral cluster temperature were estimated.;The results of metal oxide clusters experiments and calculations suggest that SO2 can be reduced and oxidized by oxygen deficient and oxygen rich vanadium oxide clusters, respectively. Three SO3 formation mechanisms are proposed, and several condensed phase catalytic cycles are suggested based on SO3 formation mechanisms. Other experiments showed that C=C bonds of alkenes can be broken on neutral vanadium oxide oxygen rich clusters with the general structure VO3(V2O 5)n=0,1,2.... DFT calculations provide a mechanistic explanation for the general reaction in which the C=C double bond of alkenes are broken. New results also help to elucidate the selective catalytic reduction of NO using NH3 on a vanadium oxide catalyst. A separate set of experiments to identify capping layer materials for extreme EUV optical coatings that are resistive to carbon contamination. Results show that oxidized Hf and Zr are much less reactive than Ti or Si oxide, and might lead to capping layers that might extend lifetimes of EUV mirror coating upon EUV irradiation. Zr oxide was found to be less reactive than Hf oxide.;The set of results demonstrate the potential of compact soft-ray lasers as new tools for chemistry and photo-physics studies with intense soft x-ray light in small laboratory environments.
机译：本文报道了一种使用新型质谱方法研究团簇的结构和反应性的方法，其中电离是由台式软X射线（SXR）激光产生的高能光子产生的。这项工作的动机是催化过程对提高气相化学反应速率的重要性，例如烃，聚合物，药物，硫酸，肥料，农药等的生产，多种形式的污染控制，强大的控制能力。用于极紫外（EUV）光刻的镜面涂层，以及用于清洁能源应用的氢存储。大量的质谱研究表明，气相纳米团簇是研究本体相中表面反应的有效模型系统。但是，使用多光子电离或电子碰撞电离源会导致团簇碎裂，从而限制了有关中性团簇母体的信息。我们的方法使用紧凑型毛细管放电驱动激光器的26.5 eV光子通过单光子事件电离簇，避免了与多光子电离相关的簇碎裂。高光子能量还可以检测具有高电离能的中性簇和小分子反应产物。;对包括范德华簇，金属氧化物和金属氧化物反应在内的几种类型的簇进行了实验。密度泛函理论（DFT）计算用于阐明团簇的几何形状，性质和反应机理。对于氢/范德华簇，计算了涉及一个中性分子损失的反应的单分子解离速率常数，并估算了中性簇温度。缺乏和富氧的钒氧化物簇。提出了三种SO3的形成机理，并基于SO3的形成机理提出了几个冷凝相催化循环。其他实验表明，在结构为VO3（V2O 5）n = 0,1,2 ...的中性氧化钒富氧簇上，烯烃的C = C键可以断裂。DFT计算为一般反应提供了机理解释其中烯烃的C ＝ C双键被破坏。新的结果也有助于阐明在氧化钒催化剂上使用NH3选择性还原NO的方法。一组单独的实验，用于识别抗碳污染的极端EUV光学涂层的覆盖层材料。结果表明，氧化的Hf和Zr的反应性远低于Ti或Si氧化物，并可能导致覆盖层，从而延长EUV镜面涂层在EUV照射下的寿命。发现Zr氧化物的反应性不如Hf氧化物。该组结果证明了紧凑型软射线激光器作为在小型实验室环境中使用强柔和X射线光进行化学和光物理研究的新工具的潜力。

著录项

  • 作者

    Heinbuch, Scott.;

  • 作者单位

    Colorado State University.;

  • 授予单位 Colorado State University.;
  • 学科 Chemistry Physical.;Engineering Electronics and Electrical.;Physics Optics.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 473 p.
  • 总页数 473
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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