C_4H_5N—(H_2O)_n氢键团簇的多光子电离与从头计算研究  

Multiphoton Ionization and ab initio Calculation Studies of the Hydrogen-Bonded Clusters C_4H_5N-(H_2O)_n

作　　者：李玥 胡勇军[1] 刘向红[1] 王秀岩[1] 楼南泉[1] 

机构地区：[1]中国科学院大连化学物理研究所分子反应动力学国家重点实验室,大连116023

出　　处：《Chinese Journal of Chemical Physics》2000年第1期11-19,共9页化学物理学报（英文）

基　　金：国家自然科学基金

摘　　要：在３５５、５３２ｎｍ激光波长下用ＴＯＦ质谱研究了Ｃ４Ｈ５Ｎ－（Ｈ２Ｏ）ｎ氢键团簇体系的多光子电离。二波长下均得到一系列Ｃ４Ｈ５Ｎ-（Ｈ２Ｏ）ｎ＋及质子化产物Ｃ４Ｈ５Ｎ-（Ｈ２Ｏ）ｎＨ＋。３５５ｎｍ下可能存在双光子共振电离过程，使得该波长下吡咯母体及团簇离子信号较５３２ｎｍ有明显增强。从头计算结果表明质子化产物的质子更可能连接于吡咯环的α-Ｃ原子，而不是Ｎ原子上，即光电离过程诱发了一个簇内的质子转移反应。在５３２ｎｍ下质子化产物的生成主要来自于一个发生于团簇内部的Ｐｅｎｎｉｎｇ电离或电荷转移过程。团簇的形成对吡咯光解产物的稳定化作用使得团簇系列Ｃ４Ｈ４Ｎ-（Ｈ２Ｏ）ｎ＋出现反常强度变化。The multiphoton ionization of the hydrogen-bonded clusters C_4H_5N-(H_2O)_n was studied using a time-of-flight mass spectrometer at 355nm and 532nm laser wavelengths. At both wavelengths, a series of C_4H_5N-(H2O)_n+ and the protonated products C_4H_5N- (H_2O)_nH^+ were obtained. The two-photon resonance ionization processes at 355nm make the ion intensities of pyrrole and the clusters obviously more abundant than at 532nm. Ab initio calculations show that in the protonated products, the proton prefers to link with a-C of pyrrole rather than with the N atom. The production of the protonated products needs an intracluster proton transfer reaction. The protonated products obtained at 532nm are suggested to arise from an intracluster penning ionization or a charge transfer process. The abnormally higher intensities of photofragments C_4H_4N-(H_2O)_n^+ (n>1) than C_4H_4N^+ are attributed to the stabilization effects of the cluster formation on the dissociation products C_4H_4N^+ of the pyrrole molecule.

关 键 词：氢键团簇 吡咯 光电离 从头计算 质子转移 

分 类 号：O641[理学—物理化学]