Laboratory studies of Criegee radical reactions

进入大气层的化学品有多种来源，但从广义上讲，要么来自人类活动，要么来自生物圈（自然系统）。当然，这些化学物质一旦进入大气层，会发生什么变化是非常重要的。如果它们是有毒的，它们会影响人类、动物和自然生态系统的健康。因此，我们必须了解污染物是如何被大气层清除的。一个非常重要的去除过程涉及所谓的羟基自由基。这是一种非常活泼的物种，就像化学洗涤剂一样，破坏污染物并清洁大气。最近的研究表明，羟基自由基的一个重要来源必须来自Criegee自由基。然而，这些Criegee激进分子直到最近才被测量出来。我们利用美国的一个设施进行的工作，使我们能够首次观察到Criegee激进分子。在这个项目中，我们将开发一个最先进的实验系统，使我们能够研究Criegee自由基的化学性质，从而帮助我们了解它们如何影响大气中存在的羟基自由基的数量。这项工作不仅将提高我们对城市环境的认识，而且还将对气候研究产生影响。Criegee中间体在很宽的压力和温度范围内的反应在大气化学中具有重要意义。拟议的UV-PE仪器将是同类仪器中的第一台，将使我们能够进行一系列实验来研究这些自由基的反应，据我们所知，世界上没有其他人可以做到。为了证明该装置的多功能性，我们提出了一套精心设计的实验，以研究对流层中Criegee自由基的来源和命运。所研究的反应的量子化学计算将提供对其机制的详细了解，动力学数据将被纳入描述对流层的模型中，并与现有的测量结果进行比较。

Chemicals entering the atmosphere come from a number of sources, but in broad terms are either from human activity or from the biosphere (natural systems). What happens to these chemicals once in the atmosphere is very important of course. If they are toxic they can impact on the health of humans, animals and natural ecosystems. Therefore, it is vital that we understand how pollutants are removed by the atmosphere. One very important removal process involves the so called hydroxyl radical. This is an extremely reactive species that acts like a chemical detergent, destroying pollutants and cleaning up the atmosphere. It has emerged in recent investigations that an important source of the hydroxyl radical must be coming from Criegee radicals. However, these Criegee radicals have been impossible to measure until recently. Work carried out by us, using a facility in the USA, has allowed us to observe a Criegee radical for the first time. In this project we will develop a state-of-the-art experimental system that will allow us to investigate the chemistry of Criegee radicals and therefore to help us to understand how they affect the amount of hydroxyl radical is present in the atmosphere. Such work will not only improve our understanding of the urban environment but will also have implications for climate studies as well. Reactions of Criegee intermediates, over a wide range of pressure and temperature, are of importance in atmospheric chemistry. The proposed UV-PE apparatus will be the first of its kind and will enable us to carry out a range of experiments to study reactions of these radicals that, as far as we are aware, no one else in the world can do. To demonstrate how versatile the apparatus is we propose a carefully designed set of experiments to look at the source and fate of Criegee radicals in the troposphere. Quantum chemistry calculations of the reactions studied will provide detailed understanding of their mechanisms and the kinetic data will be incorporated into models describing the troposphere and compared with available measurements.