Contributions to Atmospheric Chemistry by Photochemical Reactions of Cluster Molecules

分子的小聚集体通常具有独特的性质，与它们各自分离的分子或体相不同。最简单的聚集体是两个分子的络合物或二聚体。大气中的二聚体浓度预计很低，但它们的数量可能足以影响某些大气化学过程。人们对含有与大气相关的物种的二聚体的性质知之甚少。该项目将探索一种假设，即弱结合分子二聚体的光解可能是一些大气物种的重要来源。这项研究将使用两种传统方法，即在不同分压和温度下测量气体混合物光解的量子产率，以及使用傅里叶变换光谱和多光子电离与质谱学检测相结合的超音速喷射膨胀方法。这种方法将获得基本的物理参数，如吸收光谱的位移、吸收截面、二聚体结合能和形成熵。所获得的数据将直接应用于大气化学的计算机模型。

Small aggregates of molecules often have properties unique and different from their respective isolated molecules or bulk phase. The simplest aggregate is the two molecule complex or dimer. Low concentrations of dimers are expected in the atmosphere, but their numbers may be sufficient to influence certain atmospheric chemical processes. Little is known about the properties of dimers containing species of atmospheric relevance. The project will explore the hypothesis that the photolysis of weakly bound molecular dimers may be an important source for some atmospheric species. The study will use both conventional methods in which quantum yields are measured for photolysis of gas mixtures at a variety of partial pressures and temperatures and the method of supersonic jet expansion with Fourier Transform spectroscopy and multiphoton ionization coupled with mass spectrometric detection. This approach will obtain fundamental physical parameters such as shifts in absorption spectra, absorption cross-sections, dimer binding energies, and entropies of formation. The data obtained will be directly applicable to computer models of atmospheric chemistry.