Kinetics and spectroscopy of free radical intermediates in tropospheric reactions

在这项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，加州理工学院的大村光雄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理。大村教授将利用现代实验物理工具和科学推理为他的研究生提供出色的培训。他们将利用快速激光光谱技术来检测自由基物种，并观察它们在大气氧化过程中发生的变化。该奖项将通过大学内部、其他三所大学和两个政府资助的研究实验室之间的合作，为建设国家的科学基础设施做出贡献。还将扩大与法国国家同步加速器的个人的国际合作。在鼓励妇女和代表不足的少数群体参与方面，大村教授有着被证明的记录，这一点将通过扩大与当地K-12学校教室的正式联系，通过与代表不足的群体进行接触而得到加强。大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。这项工作集中于表征过氧基的命运，过氧基是大气氧化中普遍存在的中间体。这些物种的研究将使用许多技术：腔衰荡光谱、多路光电离质谱学和光电子-光离子符合光谱学。这些互补的方法旨在充分揭示过氧基如何在大气机制中演变，并表征它们的不同化学命运如何导致光化学烟雾和二次有机气溶胶。所研究的具体系统包括来自异戊二烯的过氧基，异戊二烯是排放到对流层的最重要的非甲烷碳氢化合物，以及乙酰过氧基，其反应被认为在热带地区循环氧化剂。这项研究将定量地解决不饱和物质在大气中如何被氧化的悬而未决的问题，并将有助于理解有机气溶胶的形成和羟基自由基循环的机制。

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.