中文摘要：

含氟利昂在内的含氯化合物在太阳光辐射下解离生成破坏臭氧的游离态氯原子,是破坏大气臭氧层的主要元凶.本文利用飞行时间质谱技术及离子速度成像技术研究了氟利昂F1110（四氯乙烯）分子在800 nm飞秒脉冲光作用下的多光子解离动力学.利用飞行时间质谱探测技术,得到了四氯乙烯在800 nm飞秒激光脉冲作用下发生多光子解离产生的碎片质谱,发现了两个主要碎片离子C2Cl3＋和C2Cl2＋.对应的解离机理分别为单个C—Cl键断裂直接生产氯自由基C2Cl4＋→C2Cl3＋＋Cl和两个C—Cl键断裂C2Cl4＋→C2Cl2＋＋2Cl.利用离子速度成像技术对这两种机理产生的碎片离子进行成像,得到了C2Cl3＋和C2Cl2＋离子的速度影像.分析发现这两个碎片离子的动能分布均可由两个高斯分布曲线拟合,说明这两种解离机理分别还对应了两种解离通道.通过影像分析得到了解离的平动能分布和角向分布各向异性参数等详尽的动力学信息.通过高精度密度泛函理论计算对解离动力学进行了进一步的分析和讨论.

英文摘要：

The ozone layer which absorbs harmful solar UV radiation is an essential umbrella for human beings.However,a large number of exhausts of chlorine compounds including freon released by people in the atmosphere pose a great threat to the ozone layer.Freon dissociates into the product of chlorine radicals induced by UV sunlight radiation,which are found to be the main culprit for the destruction of atmospheric ozone.In this paper,time-of-flight mass spectrometry and velocity map imaging technique are coupled for investigating the multiphoton dissociation dynamics of Freon 1110（C2Cl4,Tetrachloroethylene） induced by ultrafast short laser pulse on a femtosecond time scale at 800 nm.Fragments mass spectra of C2Cl4 are measured by time-of-flight mass spectrometry.Together with the parent ion C2Cl4＋,two dominant fragment ions C2Cl3＋ and C2Cl2＋ are discovered in the multi-photon ionization and dissociation process in the experiment.By analyzing the above mass spectra,two corresponding photodissociation mechanisms are discussed and listed as follows： 1） C2Cl4＋→C2Cl3＋＋Cl with single C—Cl bond breaking and direct production of Cl radical; 2） C2Cl4＋→C2Cl2＋2Cl with double C—Cl bonds breaking and production of two Cl radicals.Also,ion images of these two observed fragment ions C2Cl3＋ and C2Cl2＋ are measured by velocity map imaging apparatus.The kinetic energy distributions of these two fragment ions are determined from the measured velocity map images.The kinetic energy distributions of both C2Cl3＋ and C2Cl2＋ can be well fitted by two Gaussion distributions.It indicates that both fragments C2Cl3＋ and C2Cl2＋ are from two production channels.The peak energies for each channel are fitted.More detailed photodissociation dynamics is obtained by analyzing the angular distribution of the generated fragment ions.The anisotropy parameter β values are measured to be 0.46（low energy channel） and 0.52（high energy channel） for the fragment C2Cl3＋,and 0.41（low energy channel） and 0.