Kinetic Studies of Isoprene Derived Peroxy Radicals

有机化合物异戊二烯是一种极其重要的自然排放物质，在区域和全球尺度上对对流层的化学成分有贡献。光化学降解的细节已经研究了一段时间，但我们对特定过程的速率系数和机制的理解仍然存在空白，特别是在低氮氧化物（NOx）浓度条件下。这项研究将结合两个机构（纽约州立大学环境科学与林业学院和密西西比州立大学）在以下方面的专业知识：(1)产生特定异二烯衍生的过氧自由基（RO2）；(2)基于近红外光谱区腔衰荡光谱（CRDS）的新检测方法。该项目的任务是产生由羟基自由基（OH）对异戊二烯的攻击产生的过氧自由基，分配特定异构体的光谱，并确定吸收截面。然后量化这些过氧自由基与NO（一氧化氮）、HO2（羟基自由基）以及自由基自身反应的速率系数。根据这些动力学数据，将评估各种产品渠道的分支比率。此外，将详细的量子化学计算结果与实验结果进行比较，以建立预测的构效关系。这项研究的结果将导致改进大气中异戊二烯降解的化学机制，从而改进不同复杂程度的化学运输模型。相关化合物（如1,3-丁二烯、2-甲基-3-烯-2-醇和萜烯）的化学性质也将通过本研究的结果得到更好的理解。因此，考虑到这些物种对全球大气的氧化能力有极大的影响，全球大气的氧化能力将得到更好的限制。总之，这项工作将提高对异戊二烯及其相关物质的大气化学的认识。教育方面很重要，因为一名研究生、一名博士后和几名本科生将在激光光谱学、动力学、大气和量子力学建模以及生物圈-大气相互作用等领域接受培训。此外，将促进研究机构（纽约州立大学环境科学与林业学院和密西西比州立大学）之间的合作。

The organic compound, isoprene, is an extremely important, naturally emitted species that contributes to the chemistry of the troposphere on regional and global scales. The details of the photochemical degradation have been studied for some time, but there remain gaps in our understanding of rate coefficients and mechanisms of specific processes, particularly under conditions of low oxides of nitrogen (NOx) concentrations. This study will link expertise at two institutions (State University of New York College of Environmental Science and Forestry, and Mississippi State University) in (1) producing specific isoprene derived peroxy radicals (RO2) with (2) new detection methods based on cavity ring down spectroscopy (CRDS) in the near infrared spectral region. The tasks of this project are to produce peroxy radicals that are generated from the attack of hydroxyl radicals (OH) on isoprene, assign spectra to particular isomers, and determine absorption cross sections. Then rate coefficients for the reactions of these peroxy radicals with NO (nitric oxide), HO2 (hydroperoxyl radicals), as well as the radical self reaction, will be quantified. From these kinetic data, branching ratios to various product channels will be assessed. In addition, results of detailed quantum chemical calculations will be compared with the experimental results in order to develop predictive structure-activity relationships.The results of this research will lead to improved chemical mechanisms for isoprene degradation in the atmosphere, thereby improving chemical transport models of various degrees of sophistication. The chemistry of related compounds (e.g. 1,3-butadiene, 2-methyl-but-3-en-2-ol, and terpenes) will also be better understood through results of this research. The oxidizing capacity of the global atmosphere will thus be better constrained, given that these species together have an extremely large influence on it. In short, this work will improve understanding of the atmospheric chemistry of isoprene and related species. The educational aspects are significant, since a graduate student, a postdoctoral fellow, and several undergraduate students will be trained in areas of laser spectroscopy, kinetics, atmospheric and quantum mechanical modeling, and biosphere-atmosphere interactions. In addition, collaboration between the investigator's institutions (SUNY College of Environmental Science and Forestry, and Mississippi State University) will be fostered.