Photodissociation-Photoionization Mass Spectrometry

该项目属于分析和表面化学的一般领域，以及质谱学的子领域。在这项为期三年的持续资助期间，约翰斯顿教授和他的学生将使用最近发展的光解离-光电离质谱(PDPI/MS)技术来研究有机分子在气相中的光化学反应机理。在PDPI/MS中，中性分子被紫外光脉冲激光光解。第二个脉冲激光产生相干的真空紫外线辐射，然后电离母分子和来自初始激光脉冲的中性光产物。然后用四极质谱计检测产生的离子。这项研究的两个主要目标是：(1)开发改进的实验方法，利用PDPI/MS进行创新的光化学测量；(2)对有机大分子的分解机理进行基础研究。这个项目的目标的成功实现将为理解大的有机分子如何经历气相光碎裂提供一个合理的框架。这一知识将有助于快速和可靠地确定具有重要技术意义的复杂分子结构。

This project is in the general area of analytical and surface chemistry and in the subfield of mass spectrometry. During the tenure of this three-year continuing grant, Professor Johnston and his students will use the recently developed technique of photodissociation-photoionization mass spectrometry (PDPI/MS) to investigate mechanisms of photochemical reactions of organic molecules in the gas phase. In PDPI/MS, neutral molecules are photodissociated with an ultraviolet pulsed laser beam. A second pulsed laser generates coherent vacuum ultraviolet radiation which then ionizes the parent molecules and neutral photoproducts from the initial laser pulse. The resulting ions are then detected with a quadrupole mass spectrometer. The two primary goals of this research, which builds upon accomplishments of the Johnston group under NSF grant CHE-9096266, are the (1) development of improved experimental methods for making innovative photochemical measurements by PDPI/MS and (2) fundamental studies of mechanisms of decomposition of large organic molecules. %%% The successful attainment of the goals of this project will provide a rational framework for understanding how large organic molecules undergo gas phase photofragmentation. This knowledge will facilitate the rapid and reliable determination of the structures of technologically important complex molecules.