物理化学学报 >> 2004, Vol. 20 >> Issue (04): 344-349.doi: 10.3866/PKU.WHXB20040402

研究论文 上一篇    下一篇

溴代烷烃在紫外波段的光解离过程

唐颖;姬磊;唐碧峰;朱荣淑;张嵩;张冰   

  1. 中国科学院武汉物理与数学研究所，波谱与原子分子物理国家重点实验室，武汉　430071
  • 收稿日期:2003-09-11 修回日期:2003-11-17 发布日期:2004-04-15
  • 通讯作者: 张冰 E-mail:bzhang@wipm.ac.cn

Photodissociation of Alkyl Bromides at UV Scope

Tang Ying;Ji Lei;Tang Bi-Feng;Zhu Rong-Shu;Zhang Song;Zhang Bing   

  1. State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, Wuhan Institute of Physics and Mathematics, Wuhan　430071
  • Received:2003-09-11 Revised:2003-11-17 Published:2004-04-15
  • Contact: Zhang Bing E-mail:bzhang@wipm.ac.cn

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摘要： 在飞行时间质谱仪中，采用波长为234 nm和267 nm的激光，研究溴代烷烃CHBr3、CH2Br2、C2H5Br及C2H4Br2的光离解过程.在UV激光的作用下，溴代烷烃分子主要发生的是吸收1个光子解离出Br原子，然后继续吸收光子发生Br原子的（2＋1）共振增强多光子电离的过程.其中由溴代烷烃分子解离得到的Br原子可能存在着两种布居：基态Br(2P03/2)及激发态Br*(2P01/2).研究解离得到的Br原子的分支比 N(Br*)/N(Br)，并给出测量结果：溴代烷烃分子解离得到的Br原子在267 nm激光作用下的分支比明显大于在234 nm激光作用下的结果.对此多光子过程的机理，也进行了分析讨论.

关键词: 溴代烷烃, 共振增强多光子电离, 飞行时间质谱, 分支比

Abstract: Some alkyl bromides (CHBr3, CH2Br2, C2H5Br, C2H4Br2) have been studied at 234 nm and 267 nm in the time-of-flight mass spectrometer by means of multiphoton dissociation and ionization. Under the radiation of UV laser, alkyl bromides are photolyzed after absorbing one photon, release Br atoms, absorbing photons continuously, and (2＋1)resonance-enhanced multiphoton ionization of Br atoms takes place. The Br atoms from the dissociation of the bromides are probably at the ground state Br(2P03/2) or at the excitated state Br*(2P01/2),and the branching ratio of Br atom N(Br*)/N(Br) is obtained. We find that the branching ratio at 267 nm is obviously bigger than the result at 234 nm. After discussing the mechanics of the multiphoton process, we conclude that the change tendency of the branching ratio with the wavelength is due to the different dissociation channels.

Key words: Alkyl bromide, REMPI (resonance-enhanced multiphoton ionization), TOF-MS (time-of- flight mass spectrometer), Branching ratio