RUI: Decomposition of Organic Pollutants Using Electron Beams: A Theoretical Investigation

大气和土壤退化与化石燃料燃烧排放的污染物密切相关。这些污染物，主要是挥发性有机化合物，是有毒气体，参与地面臭氧的形成，并导致平流层臭氧层耗损。工业、发电站和车辆排放的主要有毒气体是氮氧化物（NOx）和二氧化硫（SO2）。氮氧化物可以很容易地在空气中转化为气态硝酸和其他有机硝酸盐，从而在大气中产生不可吸入的颗粒水平。二氧化硫本身就是一种主要的空气污染物，对环境和包括人类在内的动物生命也有类似的负面影响。脉冲电子束最近被提议用于清理发电厂的排放物，因此代表了一种有前途的廉价技术，可以在燃烧水平上清除有毒分子，而不会产生任何副产品。当电子束中的电子与NOx或SO2分子碰撞时，它可以被捕获形成一个暂时的负离子，最终导致不稳定的分子解离，这一过程被称为“解离电子附着”。目前的项目旨在研究脉冲电子束如何有效地引起这些有毒气体的解离，从而减少它们的排放。在这个项目结束时，我们希望能够提高对这些反应的理解，并为未来使用电子束清洁危险气体排放的技术铺平道路。同时，该项目将为本科生提供学习和参与最先进的计算量子化学技术的培训和教育机会。研究人员将研究NO2和SO2的解离电子附着机制，从电子捕获步骤一直到解离碎片的动力学。这项研究将提供横截面及其与分子初始振动状态的依赖关系。为了获得横截面，分子的电子结构和暂时的负分子离子状态将被表征。然后，这些计算的结果将用于构建系统可能采取的能量路线，以便解离。计算还将用于计算分子碎片的角分布，并将结果与具有高角分辨率的碎片检测实验工作进行比较。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Atmosphere and soil degradation is strongly related to emission of pollutants from combustion of fossil fuels. These pollutants, mainly volatile organic compounds, are toxic gases that participate in the formation of ground level ozone and cause stratospheric ozone layer depletion. The main toxic gases emitted by industry, power stations, and vehicles, are Nitrogen oxides (NOx) and Sulphur dioxide (SO2). Nitrogen oxides can be easily converted into gaseous nitric acid and other organic nitrates in the air contributing to irrespirable particle levels in the atmosphere. SO2 is itself a major air pollutant with similar negative impacts on the environment and animal life, including humans. Pulse electron beams have recently been proposed to clean up emissions from power plants, thereby representing a promising and cheap technique to scrub toxic molecules at combustion level without any byproducts. As an electron from the beam collides with a NOx or SO2 molecule, it can be captured forming a temporary negative ion, eventually leading to instabilities responsible for molecular dissociation in a process known as "dissociative electronic attachment." The present project aims to investigate how effectively pulse electron beams can cause the dissociation of these toxic gases thereby reducing their emission. At the end of this project we expect to have improved the understanding of these reactions and paved the way for future techniques to clean dangerous gas emissions using electron beams. At the same time, the project will create training and educational opportunities for undergraduate students to learn and get involved in state-of-the-art computational quantum chemistry techniques.The researchers will study the dissociative electronic attachment mechanism of NO2 and SO2, from the electron capture step all the way to the dynamics of the dissociating fragments. This research will provide cross sections and their dependence on the initial molecular vibrational state. In order to obtain the cross sections, the electronic structure of the molecule and the temporary negative molecular ion states will be characterized. Then, the results of these calculations will be used to construct the possible energetic routes the system can take in order to dissociate. The calculations will also be used to compute angular distribution of the molecular fragments, and the results will be compared against experimental works with high angular resolution of fragment detection.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.