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首页> 外文学位 >A. Computational chemistry applied to the analysis of air pollution reaction mechanisms. B. Fundamental studies of droplet evaporation and discharge dynamics in electrospray ionization.
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A. Computational chemistry applied to the analysis of air pollution reaction mechanisms. B. Fundamental studies of droplet evaporation and discharge dynamics in electrospray ionization.

机译：A.计算化学应用于空气污染反应机理的分析。 B.电喷雾电离中液滴蒸发和放电动力学的基础研究。

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摘要

The first part of the thesis investigates the use of theoretical quantum chemical calculations in studying the pathways for the atmospheric aromatic-OH reaction. The computational model is comprised of a semi-empirical PM3 geometry optimization followed by a single point calculation using density functional theory (Becke3LYP/6-31G(d,p)). Full mechanisms for the OH-initiated photooxidation of toluene, m-xylene, p-xylene, 1,2,4-trimethylbenzene and m-ethyltoluene are developed. The lowest energy intermediates are determined and predicted products from these structures compared to available experimental product data. These studies serve to refine proposed mechanisms currently available for toluene, m-xylene and p-xylene, while providing new information on the 1,2,4-trimethylbenzene and m-ethyltoluene reaction pathways.;The second part reports the application of a technique for probing the dynamics of charged droplet evaporation and discharge in electrospray ionization. Charged droplets from an electrospray are injected into a cylindrical drift cell, in which a phase Doppler anemometer (PDA) measures the diameter and charge of individual droplets. After initial detection and characterization, the electric field within the cell is repeatedly reversed to pass the droplet through the measurement volume of the PDA. This "ping-pong" experiment yields the size and charge of a single droplet as a function of time. We applied this technique to solvents used commonly in electrospray, and report the following observations: (1) The discharge dynamics of droplets with the same initial diameter and charge are highly reproducible for all solvents and analyte/solvent combinations studied to date, in temporal patterns dictated by solvent evaporation and the approach to the Rayleigh limit of charge. (2) Droplet discharge events occur at, or slightly above, the Rayleigh limit of charge, and are characterized by loss of 15--30% of the charge from methanol, acetonitrile and water droplets, with little accompanying loss of solvent. (3) The addition of biomolecules or salt (up to 10--3 M) to the solution does not significantly alter discharge dynamics. (4) Droplet polarity does not influence discharge dynamics. (5) No significant displacement of the droplet arises from discharge events. (6) Droplet size-charge correlations show that, in certain instances, droplets from an electrospray fall into discrete groupings that can be attributed to fission events.
机译：本文的第一部分研究了理论量子化学计算在研究大气芳香族-OH反应途径中的应用。该计算模型由半经验的PM3几何优化和随后的使用密度泛函理论（Becke3LYP / 6-31G（d，p））的单点计算组成。建立了OH引发甲苯，间二甲苯，对二甲苯，1,2,4-三甲基苯和间乙基甲苯的光氧化反应的全部机理。与可用的实验产品数据相比，从这些结构中确定并预测了最低能量的中间体。这些研究有助于完善目前对甲苯，间二甲苯和对二甲苯可用的拟议机理，同时提供有关1,2,4-三甲基苯和间乙基甲苯反应途径的新信息。第二部分报道了该技术的应用用于探测电喷雾电离中带电液滴蒸发和放电的动力学。来自电喷雾的带电液滴被注入到圆柱形漂移池中，其中相位多普勒风速计（PDA）测量单个液滴的直径和电荷。初始检测和表征后，细胞内的电场反复反转，使液滴通过PDA的测量空间。该“乒乓”实验得出单个液滴的大小和电荷随时间的变化。我们将该技术应用于电喷雾中常用的溶剂，并报告了以下观察结果：（1）到目前为止，在时间模式下，对于所有已研究的所有溶剂和分析物/溶剂组合，具有相同初始直径和电荷的液滴的放电动力学具有高度可再现性由溶剂蒸发和接近瑞利电荷极限决定。 （2）液滴排放事件发生在瑞利电荷极限处或略高于瑞利电荷极限，其特征是甲醇，乙腈和水滴损失了15--30％的电荷，几乎没有溶剂损失。 （3）向溶液中添加生物分子或盐（最多10--3 M）不会显着改变放电动力学。 （4）液滴的极性不影响放电动力学。 （5）没有由于排出事件引起液滴的明显位移。 （6）液滴大小与电荷的相关性表明，在某些情况下，来自电喷雾的液滴会分成可归因于裂变事件的离散组。

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  • 作者

    Smith, James Norman.;

  • 作者单位

    California Institute of Technology.;

  • 授予单位 California Institute of Technology.;
  • 学科 Chemistry Analytical.;Physics Atmospheric Science.
  • 学位 Ph.D.
  • 年度 2000
  • 页码 303 p.
  • 总页数 303
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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