氨/胺促进大气成核机制的红外光解离谱研究

In order to understand the physical and chemical behavior of aerosols and to predict their climatic, ecological and environmental effects, it is significant to understand the mechanism of the atmospheric new particle formation. NH3 and amines extensively exist in the atmospheric environment, and can be combined with sulfuric acid molecules to form acid-base pairs, resulting in the reduction of the evaporation of clusters and enhanced nucleation. Recent researches indicate that the formation rate of atmospheric ternary homogeneous nucleation involved ammonia/amine is much higher than that of binary homogeneous nucleation, which implies that ammonia/amine may play an important role in the atmospheric new particle formation. However, the micro-physicochemical mechanisms of atmospheric new particle formation involved NH3/amine remain unclear. For example, the information of cluster composition and structure in the critical nucleation process of NH3/amines-H2SO4-H2O system has not been directly observed; and the mechanism of atmospheric new particle formation is still debatable. This proposal takes the infrared photodissociation spectroscopy technique combining with ab initio quantum chemistry, molecular dynamics simulation and theoretical infrared spectra calculation to determine the composition and structural information of a series clusters of NH3/amine-H2SO4-H2O during the nucleation process. The composition and structure of the stable initial cluster during the nucleation of NH3/amine-H2SO4-H2O are determined and in-depth analyzed. In addition, based on the structural characteristics and theoretical transition state calculation, the effect of temperature on the nucleation mechanism of NH3/amine-H2SO4-H2O is discovered. This research would aid in the improvement of the multi-scale prediction model for nucleation/aerosol/climate.

深入理解大气新粒子的生成机制，对预测其气候、生态和环境效应都具有重要意义。氨、胺广泛存在于大气环境中，能够与硫酸分子结合形成酸碱对，降低团簇的蒸发，从显著提高新粒子的成核速率。研究显示，氨/胺参与的三元大气成核速率远高于传统的二元成核模型，可能对大气新粒子形成具有重要的贡献。然而，NH3/胺参与的新粒子生成的微观物理化学机制仍有待研究。例如，NH3/胺-H2SO4-H2O体系初始成核的团簇组分和结构尚无定论；关于成核机制，也存在较多争议。本项研究拟采用变温红外光解离谱技术，结合量子化学从头计算、分子动力学模拟和团簇红外光谱理论计算，确定NH3/胺-H2SO4-H2O体系成核过程中一系列产物团簇的组分和结构信息，深入探索成核过程中稳定初始团簇的组分与结构；同时基于成核团簇的结构特征和过渡态计算，分析团簇生长机制，以及温度效应对成核路径的影响，为成核/气溶胶/气候多尺度预测模型的完善提供参考。

深入理解大气新粒子的生成机制，对预测其气候、生态和环境效应都具有重要意义。氨/胺广泛存在于大气环境中，能够与硫酸分子结合形成酸碱对，降低团簇的蒸发，从而显著提高新粒子的成核速率。研究显示，氨/胺参与的三元大气成核速率远高于传统的二元成核模型，可能对大气新粒子形成具有重要的贡献。然而，氨/胺参与的新粒子生成过程的微观物理化学机制仍有待研究。本项目研究了大气中氨和典型有机胺分子在新粒子成核过程中的初始构型和成核机制。我们通过调控离子阱中气相团簇的温度，测试了NH3-H2SO4-H2O体系形成的团簇的变温质谱数据，实验结果表明在环境温度大于100 K时，成核过程中稳定初始团簇的形成最有利。此外，我们还利用变温红外光解离谱技术测试了这些稳定初始团簇的红外预解离光谱。结合全局低能构型搜索、量子化学从头计算、分子动力学模拟和团簇红外光谱理论计算方法，分析了这些团簇的组分信息和结构信息，并深入分析了该体系的成核机制，以及环境温度对成核机制的影响。此外，我们通过全局低能构型搜索和量子化学从头计算研究了大气中常见有机胺（甲胺、二甲胺、三甲胺、二乙胺）和有机酸（甲磺酸、草酸、乙酸、2-甲基甘油酸、3-羟基-4,4-二甲基戊二酸）在H2SO4-H2O体系的初期成核过程中的稳定初始团簇的结构与热力学性质，并基于这些热力学数据和大气团簇动力学模拟方法分析了它们在新粒子形成中的贡献和作用。