基于阈值光电子- - 光离子符合技术的碳氢自由基光电离和光解离电离研究

Hydrocarbon radicals occur as important intermediates in reactive environments like combustion, the atmosphere or interstellar space, and play central roles in many chemical reactions. Utilizing vacuum ultraviolet synchrotron radiation as light source, photoionization and disociative photoionization studies of hydrocarbon radicals will be proposed in the project to be carried out with the technique of threshold photoelectron-photoion coincidence, which is also a novel method to be used to detect and investigate free radicals. Then the spectrscopy, structure and dissociative dynamics of hydrocarbon radical ions can be obtained in experiments. Many useful data such as the ionization energies of hydrocarbon radicals, adiabatic appearance energies of fragment ions, kinetic energy released distribution and angular distribution in dissociation can be accuratly acquired from mass-selected threshold photoelectron-photoion coincidence spectra ,coincidence time-of-flight mass spectra and coincidence velocity images. In addition, with the aid of theoretical calculation, the dissociation mechanism of free radical ions will be revealled too. The present research will definitely provide both experimental and theoretical foundations for the investigations of free radicals and reactions in the above extreme environments.

碳氢自由基广泛存在于燃烧火焰、地球大气层和星际空间之中，是很多化学反应的中间体，在化学反应中起着至关重要的作用。本项目运用阈值光电子-光离子符合技术和同步辐射光源，开展碳氢自由基的真空紫外光电离和光解离电离实验研究，通过获得具有质量选择的阈值光电子- - 光离子符合光谱、符合质谱和符合图像，发展新的自由基检测和研究方法，获知碳氢自由基离子的光谱、结构和解离动力学行为，并精确测量碳氢自由基的电离能、碎片离子出现势、平动能分布和角向分布等信息，揭示自由基离子的解离机理，为深入认识和理解上述极端环境下的自由基及其反应提供实验和理论支持。

自由基是化学反应中重要的中间体，在化学反应过程中扮演着极其重要的角色。本项目的研究过程中，我们以同步辐射真空紫外光作为电离源，通过研制闪光热解自由基反应装置，结合前期已经建立的阈值光电子光离子符合成像质谱仪，发展了基于符合技术的自由基检测和研究方法；开展了CH3、C2H5、C3H7和C7H7等碳氢自由基的阈值光电子光离子符合实验研究，获得了具有质量选择的阈值光电子光离子符合光谱和符合质谱，精确测量了自由基的电离能和离子振动频率等基本数据，并对自由基的分子和离子结构进行了分析；还开展了若干自由基母体分子的光解离电离动力学研究，获得了高能量分辨的阈值光电子谱和符合图像，精确测量了碎片离子的出现势、平动能和角向分布等信息，揭示了其具有量子态选择的离子解离机理。