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首页> 外文学位 >Cavity ring-down spectroscopic study of gas-phase photolysis of unsaturated dicarbonyls and aromatic aldehydes, and surface photolysis of acetaldehyde.
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Cavity ring-down spectroscopic study of gas-phase photolysis of unsaturated dicarbonyls and aromatic aldehydes, and surface photolysis of acetaldehyde.

机译：腔衰荡光谱研究不饱和二羰基化合物和芳族醛的气相光解以及乙醛的表面光解。

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摘要

Photochemical smog is a phenomenon associated with pollution in urban atmospheres arising from the photochemical oxidation of volatile organic compounds (VOCs) in the presence of nitrogen oxides. The oxidation process can lead to ozone and secondary air pollutants including particle formation which reduce visibility. The term "photochemical smog" is used to describe this pollutant mixture. The further degradation of secondary air pollutants could also have an impact on the atmospheric oxidation capacity. However, the atmospheric degradation mechanisms of the secondary pollutants are still not fully understood. In this dissertation, cavity ring-down spectroscopy combined with laser photolysis and Fourier transform infrared spectroscopy have been employed to investigate gas-phase photolysis of unsaturated dicarbonyls and aromatic aldehydes, and surface photolysis of acetaldehyde. The unsaturated dicarbonyls studied included trans/cis-4-oxo-2-pentenal and E,E-2,4-hexadienedial, which have been observed as ring-openning products from the OH radical initiated atmospheric photo-oxidation of aromatic hydrocarbons (AHCs). The aromatic aldehydes studied included benzaldehyde and 2-nitrobenzaldehyde, which have previously been observed as ring-retaining products from atmospheric degradation of aromatic hydrocarbons.;For the gas-phase photolysis studies of trans/cis-4-oxo-2-pentenal, E,E-2,4-hexadienedial and 2-nitrobenzaldehyde, absorption cross section values in the UV/visible region and radical product quantum yields at different photolysis wavelengths have been measured or estimated. Numerous photolysis end-products have also been identified and quantified. The large differences between our measured gas-phase absorption cross sections and previously determined aqueous phase cross sections indicates that only the gas-phase cross section values should be employed in the modeling of gas-phase atmospheric chemistry of these secondary pollutants. Atmospheric photolysis pathways for these compounds have been characterized, which included photoisomerization, photocyclization, radical formation and molecular elimination. Our estimations on the atmospheric photolysis rate constants indicated that photolysis competes or supersedes OH radical reaction in removing these compounds from the atmosphere.;We have successfully employed laser photolysis combined with cavity ring-down spectroscopy to study the photolysis of acetaldehyde adsorbed on aluminum surfaces and ice films. The formyl radical (HCO) has been found to be produced from the surface photolysis and its quantum yield has been determined. Our results suggest that surface photolysis of acetaldehyde also contributes to free radical formation in the atmosphere.
机译：光化学烟雾是在存在氮氧化物的情况下由挥发性有机化合物（VOC）的光化学氧化引起的与城市大气污染相关的现象。氧化过程会导致臭氧和包括颗粒形成在内的二次空气污染物，从而降低能见度。术语“光化学烟雾”用于描述这种污染物混合物。二次空气污染物的进一步降解也可能影响大气的氧化能力。但是，仍未完全了解次级污染物在大气中的降解机理。本文采用腔衰荡光谱法结合激光光解法和傅里叶变换红外光谱法研究了不饱和二羰基和芳族醛的气相光解以及乙醛的表面光解。研究的不饱和二羰基化合物包括反式/顺式-4-氧代-2-戊烯醛和E，E-2,4-己二烯醛，它们已被观察为由OH自由基引发的芳香族烃（AHCs）的大气光氧化而开环的产物。 ）。所研究的芳族醛包括苯甲醛和2-硝基苯甲醛，它们以前被认为是大气中芳烃降解产生的环保留产物。;用于反式/顺式4-氧代-2-戊烯醛的气相光解研究，E-2,4-己二烯醛和2-硝基苯甲醛，UV /可见光区域的吸收截面值和不同光解波长下的自由基产物量子产率已得到测量或估计。还已经鉴定和定量了许多光解终产物。我们测得的气相吸收截面和先前确定的水相截面之间的巨大差异表明，在这些次要污染物的气相大气化学模型中，仅应采用气相截面值。这些化合物的大气光解途径已被表征，包括光异构化，光环化，自由基形成和分子消除。我们对大气中光解速率常数的估计表明，光解能竞争或取代OH自由基反应，从而从大气中除去这些化合物。我们已成功地利用激光光解结合腔衰荡光谱技术研究了吸附在铝表面上的乙醛的光解和冰膜。已经发现表面光解会产生甲酰基（HCO），并已确定其量子产率。我们的结果表明乙醛的表面光解也有助于大气中自由基的形成。

著录项

  • 作者

    Xiang, Bin.;

  • 作者单位

    State University of New York at Albany.;

  • 授予单位 State University of New York at Albany.;
  • 学科 Environmental Sciences.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 181 p.
  • 总页数 181
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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