时间、能量分辨的光电离质谱技术研究气相自由基反应

闪光光解流动管反应器与同步辐射光电离质谱技术两者相结合组成实验平台用于探测气相自由基反应动力学。外触发的脉冲激光光解流动管反应器内的先驱物来产生待反应的自由基;自由基与反应气体发生反应后,由流动管侧壁小孔取样、取样后的混合气体被同步辐射光电离;飞行时间质谱探测光电离产生的离子。同时脉冲信号触发脉冲发生器使其产生一连串的脉冲,间隔40~50μs,此脉冲外触发质谱的采集,连续采集覆盖单次光解反应过程。质谱的时间分辨率为40μs,满足微秒时间内探测反应动力学过程。通过同步辐射光电离反射飞行质谱能直接探测自由基反应产物,并利用光电离效率曲线获得其电离能并区分不同的异构体。实验利用光解产生Cl自由基并与1-丁烯和异丁烯反应,测得反应的加成和消除产物,并获得其加成产物的电离能。

Multiplexed time- and photon-energy-resolved photoionization mass spectrometer for kinetics of radical reactions study

A combination of flash photolysis reactor tube and synchrotron radiation photoionization mass spectrometer has been constructed for the study of the gas phase chemical kinetics. The radical-molecule chemical reactions in a side-sampled flow tubular reactor are initiated by a pulsed photolysis laser. Then the gas mixture is sampled via a pinpole and photoionized by tunable synchrotron radiation VUV photons. The constant flux ions are detected by the subsequent time-of-flight mass spectrometer. At the same time, pulsed generator generates a burst of pulses with duration of 40-50 s, which initiate the collection of mass spectrometer. The continuous collection covers the overall reaction time. The time resolution of mass spectrometer is 40 s, fulfilling the detection of transient or stable species on a millisecond time scale. In addition, the reaction products are directly detected by mass spectrometer and different structural isomers can be distinguished by photoionization efficiency curves. The experiment utilizing Cl radical reaction with 1-butene and isobutene obtains the addition and abstraction products as well as their photoionization energies.