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产生的污染物排放密切相关。这些污染物，主要是挥发性有机化合物，是参与地面臭氧形成并造成平流层臭氧层消耗的有毒气体。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）。氮氧化物在空气中很容易转化为气态硝酸和其他有机硝酸盐，导致大气中的不可呼吸颗粒物水平。二氧化硫本身是一种主要的空气污染物，对环境和动物生活（包括人类）有类似的负面影响。脉冲电子束最近被提出来清理发电厂的排放物，从而代表了一种有前途且廉价的技术，可以在燃烧水平上洗涤有毒分子而没有任何副产物。当来自光束的电子与NOx或SO2分子碰撞时，它可以被捕获，形成临时的负离子，最终导致不稳定性，导致分子在称为“解离电子附着”的过程中解离。“本项目旨在研究脉冲电子束如何有效地使这些有毒气体分解，从而减少其排放。在这个项目的最后，我们希望能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培训和教育机会，让他们学习和参与最先进的计算量子化学技术。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和它们对初始分子振动态的依赖性。为了获得截面，分子的电子结构和暂时的负分子离子状态将被表征。然后，这些计算的结果将被用来构建系统可能采取的能量路径，以离解。计算结果还将用于计算分子碎片的角分布，并与具有高角分辨率的碎片探测实验工作进行比较。该奖项反映了NSF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.