Kinetics and spectroscopy of free radical intermediates in tropospheric reactions

在这个由美国国家科学基金会化学部环境化学科学项目资助的项目中，加州理工学院的Mitchio Okumura教授正在研究形成空气污染的挥发性有机化合物的氧化机制。奥村教授将为他的研究生提供利用现代实验物理工具和科学推理的优秀培训。他们将利用快速激光光谱技术来检测自由基种类，并观察它们在大气氧化过程中如何发生变化。该奖项将通过该大学内部、其他三所大学和两个政府资助的研究实验室的合作，为建设国家的科学基础设施做出贡献。国际合作也将扩大与来自法国国家同步加速器的个人。Okumura教授在鼓励妇女和代表性不足的少数群体参与方面有着良好的记录，将通过扩大与当地K-12学校教室的正式联系，向代表性不足的群体提供服务，从而加强这一记录。奥村集团之前创建的外展项目将继续发展，向小学生传授空气污染知识，同时激发他们对科学的兴趣。这项工作的重点是表征过氧自由基的命运，这是在大气氧化无处不在的中间体。这些物质将使用许多技术进行研究：腔衰荡光谱，多路光电离质谱，光电子-光离子重合光谱。互补的方法旨在充分揭示过氧自由基如何在大气机制中进化，并表征其不同的化学命运如何导致光化学烟雾和二次有机气溶胶。研究的具体系统包括异戊二烯衍生的过氧自由基，这是排放到对流层的最重要的非甲烷碳氢化合物，乙酰过氧，其反应被认为是在热带循环氧化剂。这项研究将定量地解决关于不饱和物质如何在大气中被氧化的开放性问题，并将导致对有机气溶胶形成和羟基自由基回收机制的理解。

In this project funded by the Environmental Chemical Sciences program of the Chemistry Division at the National Science Foundation, Professor Mitchio Okumura of the California Institute of Technology is researching the oxidation mechanisms of volatile organic compounds that form air pollution. Professor Okumura will provide excellent training for his graduate students utilizing modern experimental physical tools, as well as with scientific reasoning. They will utilize fast laser spectroscopic techniques to detect free radical species and observe how changes occur as they flow through atmospheric oxidation processes. The award will contribute to building the nation's scientific infrastructure through collaborations within the university, among three other universities, and two government funded research laboratories. International collaboration will also be expanded with individuals from the French National Synchrotron. Professor Okumura has a proven record in encouraging the participation of women and underrepresented minorities, which will be strengthened through outreach to underrepresented groups by the expansion of formal connections to classrooms in local K-12 schools. Prior outreach programs created by the Okumura Group will continue to be developed to teach elementary school students about air pollution while inspiring their interest in science. This work focuses on characterizing the fates of peroxy radicals, which are ubiquitous intermediates in atmospheric oxidation. These species will be studied using many techniques: Cavity Ringdown Spectroscopy, Multiplexed Photoionization Mass Spectrometry, and Photoelectron-Photoion Coincidence Spectroscopy. The complementary approaches are designed to fully reveal how peroxy radicals evolve in atmospheric mechanisms and to characterize how their diverse chemical fates can lead to photochemical smog and secondary organic aerosol. Specific systems studied include the peroxy radicals derived from isoprene, the most important non-methane hydrocarbon emitted into the troposphere, and acetyl peroxy, whose reactions are believed to recycle oxidant in the tropics. The research will quantitatively address open questions about how unsaturated species are oxidized in the atmosphere and will lead to an understanding of organic aerosol formation and hydroxyl radical recycling mechanisms.