【作者】 张锋；

【导师】 张冰；

【作者基本信息】 中国科学院研究生院（武汉物理与数学研究所） ， 原子与分子物理， 2008， 博士

【摘要】 分子的光解是一种最重要、最基本的光化学过程，研究分子的光解动力学不仪可以获得分子激发态的信息，而且有助于理解基元化学反应的本质。本文主要利用离子速度影像技术研究了几种典型卤代化合物的光解离机理。主要内容包括以下几个方面：（1）通过探测光解碎片I(²P_3/2)和I^*（²P（1/2））的离子速度影像，研究了1-碘丙烷和2-碘丙烷在267nm的解离动力学。结果表明，随着α-碳原子上自由基的分支化程度增大，分子关联到通道I（²（P3/2））的几率明显增大，产物的能量分布明显变宽；而对同一分子，I（²P（3/2））通道的能量分布比I^*（²P（1/2））的宽，而角度分布的各向异性却比I^*（²P（1/2））的弱。（2）利用离子速度影像技术研究了2-溴噻吩和3-溴噻吩的C-Br键在267nm的解离机理。研究表明C-Br键断裂生成Br（²（P3/2））和Br^*（²P（1/2））存在三种可能途径：（i）从单重激发态到三重激发态的快速预解离；（ii）从单重激发态无辐射跃迁到电子基态的高振动激发态，随后发生热解离；（iii）母体多光子电离后的解离。并且随着溴原子在噻吩环上的取代位置远离硫原子，来自途径（i）和（ii）产物之间的比例明显减小，相应途径的各向异性分布明显变弱。（3）利用飞秒泵浦一探测技术研究了氯溴甲烷（CH₂BrCl）的解离行为。结果表明该分子主要的光解产物为CH₂Cl⁺、CH₂Br⁺和CH₂BrCl⁺。同时获得了母体离子A-带的解离寿命，并探讨了碎片离子产牛机理。更多还原

【Abstract】 The photodissociation of molecules are one of the most important and primary processes in photochemical reactions. The studies on the photodissociation dynamics are helpful not only to obtain the information on the excited states of the molecules but also to understand the nature of the fundamental reactions. In this dissertation, we have investigated the photodissociation mechanisms of some typical Halogenated compounds using the ion velocity imaging and relevant techniques. The main work is summarized as following:（1） The photodissociation dynamics of 1-Iodopropane （1-C₃H₇I） and 2-Iodopropane （2-C₃H₇I） at 267nm have been investigated with the ion images of the photofragments I(²P_3/2) and I^*(²P_1/2). The results indicate that, with the radical on a-carbon atom being more branched, the probabilities to form the I(²P_3/2) fragments obviously increase and the energy distribution of the photoproducts become visibly wider; for the same molecule, the energy distributions of the I(²P_3/2) channels are wider than those of the I^*(²P_1/2) channels while the corresponding angular distributions are weaker than those of I^*(²P_1/2) channels.（2）The fission mechanisms of the C-Br bonds of 2-bromothiophene and 3-bromothiophene at 267nm have been investigated using ion velocity imaging technique. The results indicate that there exist three possible pathways for the fission of the C-Br bonds: （i） the fast predissociation via the transition from the singlet excited state to the triplet excited state, （ii） the thermal dissociation via the radiationless transition from the singlet excited state to the highly vibrational ground state and （iii） the fragmentation of the parent ions produced by multiphoton absorption, and with the position of Br atom in the thienyl being far from sulphur atom, the relative ratios of products from the channel （i） and the channel （ii） decrease obviously and the corresponding anisotropy of each pathway weaker.（3） The dissociative behaviors of the Chlorobromometnane （CH₂BrCl） have been investigated using femtosecond pump-probe technique. It is found that the main photoproducts of the molecule are CH₂Cl⁺,CH₂Br⁺ and CH₂BrCl⁺. The dissociation lifetime of the A-band for the parent molecule is obtained and the mechanisms to form the fragment ions are discussed.更多还原