物理化学学报 >> 2000, Vol. 16 >> Issue (09): 810-817.doi: 10.3866/PKU.WHXB20000910

研究论文 上一篇    下一篇

C4H5N-(NH3)n氢键团簇的多光子电力与从头计算

李月, 胡勇军, 吕日昌, 王秀岩   

  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
  • 收稿日期:2000-01-11 修回日期:2000-04-04 发布日期:2000-09-15
  • 通讯作者: 吕日昌

Multiphoton lonization and Ab lnitio Calculation of C4H5N-(NH3)n Hydrogen-bond Clusters

Li Yue, Hu Yong-Jun, Lv Ri-Chang, Wang Xiu-Yan   

  1. State Key Laboratory of Molecular Reaction Dynamics,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023
  • Received:2000-01-11 Revised:2000-04-04 Published:2000-09-15
  • Contact: Lv Ri-Chang

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摘要：

在355和532nm激光波长下用TOF质谱仪研究了C4H5N-(NH3)n系列氢键团簇体系的多光子电离. 实验发现,两波长下除了得到一系列团簇离子外,还观测到一系列质子化产物C4H5N-(NH3)n－H＋.这些质子化产物来自于光电离过程中团簇内部的质子转移反应；系列离子出现反常强度变化,即C4H5N-(NH3)2+离子强度较C4H5N-(NH3)3+离子明显减小;从头计算结果表明,上述现象是由于中性团簇稳定性的差异造成的.

关键词: 多光子电离, 吡咯, 飞行时间, 二元团簇

Abstract:

Multiphoton ionization of binary clusters (C4H5N)－ NH3 at 355 and 532 nm have been investigated using a TOF mass spectrometer. The experimenal results showed that normal cluster ions and protonated cluster ions were produced at both laser wavelengths. The protonated products came from the intracluster proton transfer reaction. The existence of NH3 in the clusters increased the ionization cross sections of the clusters. The higher ionization efficiency at 355 nm results from the (2＋ 1) resonance multiphoton ionization of the pyrrole molecule. A peculiar low abundance of was observed, ab initio calculations indicated that when ammonia number n ≥ 3,two hydrogen bonds between ammnia chain and pyrrole ring can be formed, and the cluster become more stable. The channel ratio for the formation of protonated and unprotonated products increases with the increase of n,in agreement with the trend of proton affinity of (C4H5N)－ (NH3 )n.

Key words: Multiphoton ionization, Pyrrole, TOF-MS, Binary cluster