Photodissociation/Photoionization Mass Spectrometry

这项资助是在分析和表面化学的一般领域，以及在质谱的子领域。默里·约翰斯顿教授将研究含有4到10个碳原子的碳氢化合物分子的激光光解离和光电离。该程序的一个重要目标是确定分子被光电离后碎片化的机制。这将导致更具体的方法来确定大分子的结构，从控制碎片质谱。这将改善复杂碳氢化合物混合物的测定，如碳氢燃料和油，这是由质谱完成的。主要研究方向为紫外和真空紫外单分子光化学以及烷烃和烯烃的光解反应。主要目的是了解“软”光电离过程中电荷的远程碎片化和电荷的局部化。这种新方法将允许更可控的光破碎，并将与电子冲击和化学电离技术进行比较。气相烷烃和烯烃将被准分子激光光解离，光产物将被118 nm光子光解离。将利用飞行时间质谱检测。特定片段的相对丰度将用于理解分支。用这种方法最大限度地减少碎片的重排，可以在质谱分析中更清晰地解释结构。

This grant is in the general field of analytical and surface chemistry, and in the subfield of mass spectrometry. Professor Murray Johnston will study the laser photodissociation and photoionization of hydrocarbon molecules containing four to ten carbon atoms. An important objective of the program is to identify mechanisms of fragmentations of molecules after they have been photoionized. This will lead to more specific means of determining structure in large molecules from controlled fragmentations in mass spectrometry. This will improve the determination of complex hydrocarbon mixtures, such as hydrocarbon fuels and oils, which is accomplished by mass spectrometry. The research to be conducted will focus on ultraviolet and vacuum ultraviolet unimolecular photochemistry and photodissociation of alkanes and alkenes. The main objective is to understand charge remote fragmentation and the localization of charge in "soft" photoionization processes. This novel approach will allow for more controlled photofragmentation, and will be compared with electron impact and chemical ionization techniques. Gas phase alkanes and alkenes will be photodissociated by an excimer laser and the photoproducts photoionized by 118 nm photons. Time of Flight mass spectrometric detection will be utilized. Relative abundances of specific fragments will be used to understand branching. The minimization of rearrangements upon fragmentation with this method should allow cleaner interpretation of structure in mass spectrometry.