Investigation of Aerosol Formation and Heterogeneous Chemistry on a Molecular Level: The Reactivity, Stability, and Photochemistry of Small Clusters of Atmospheric Interest

气溶胶的形成和化学作用是大气化学的一个重要方面，但人们对它的了解仍然相对较少。通过对气相分子团簇的研究，可以获得对气溶胶的形成、随后的生长以及发生在气溶胶内部或由气溶胶催化的化学转化的相当多的知识和见解。关于团簇的信息对于确定成核前胚胎的稳定性和形成气体到颗粒转化的理论至关重要。簇还提供了一种介质，通过它可以在分子水平上详细了解非均相反应，包括金属离子和光化学过程在化学转化中的作用。该研究项目涉及三个主要领域的实验研究，这将有助于阐明上述过程的重要方面。这些研究包括：(1)缔合（聚类）反应的动力学以及聚类与大气分子的后续反应；(2)团簇的热化学性质；(3)团簇内的光化学反应、光解光谱和团簇的解离动力学。第一项研究将在一个温度可变的离子流管中进行，其中包括一个电漂移场。第二种方法采用高压离子源质谱仪，第三种方法采用具有离子能量和质量分析能力的分子束腔内激光装置。此外，计算工作涉及从头算量子力学、经典轨迹、RRKM模型和相空间理论，以增加该计划的实验阶段。

The formation and chemical role of aerosols is an important aspect of atmospheric chemistry that is still relatively poorly understood. Considerable knowledge and insight into the formation of aerosols, their subsequent growth, and the chemical transformations that occur within or that are catalyzed by aerosols can be gained through an investigation of gas-phase molecular clusters. Information on clusters is crucial for determining the stability of prenucleation embryos and formulating theories of gas-to-particle conversion. Clusters also provide a medium through which a detailed understanding of heterogeneous reactions, including the role of metal ions and photochemical processes on chemical conversions can be obtained on a molecular level. This research project involves an experimental study in three main areas which will serve to elucidate important aspects of the above mentioned processes. These include investigations of: (1) the kinetics of association (clustering) reactions and the subsequent reactions of clusters with atmospheric molecules; (2) the thermochemical properties of clusters; and (3) photochemical reactions within clusters, their photodissociation spectroscopy and the dissociation dynamics of clusters. The first investigation is to be performed with a temperature variable selected ion flow tube which includes an electric drift field. The second is conducted with a high pressure ion source mass spectrometer and the third employs a molecular beam- intracavity laser apparatus with ion energy and mass analysis capabilities. Additionally, computational efforts involving ab initio quantum mechanics, classical trajectories, RRKM models, and phase-space theory are planned in order to augment the experimental phases of the program.