物理化学学报 >> 2011, Vol. 27 >> Issue (12): 27492749-2754..doi: 10.3866/PKU.WHXB20112749

热力学,动力学和结构化学 上一篇    下一篇

氯甲烷分子在13至17 eV激发能量范围内的电离解离

吴曼曼, 唐小锋, 牛铭理, 周晓国, 戴静华, 刘世林   

  1. 合肥微尺度物质科学国家实验室筹, 中国科学技术大学化学物理系, 合肥 230026
  • 收稿日期:2011-09-21 修回日期:2011-10-09 发布日期:2011-11-25
  • 通讯作者: 周晓国 E-mail:xzhou@ustc.edu.cn
  • 基金资助:

    国家自然科学基金(10979042, 21073173)和国家重点基础研究发展规划项目(973) (2007CB815204)资助

Ionization and Dissociation of Methyl Chloride in an Excitation Energy Range of 13-17 eV

WU Man-Man, TANG Xiao-Feng, NIU Ming-Li, ZHOU Xiao-Guo, DAI Jing-Hua, LIU Shi-Lin   

  1. Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics,University of Science and Technology of China, Hefei 230026, P. R. China
  • Received:2011-09-21 Revised:2011-10-09 Published:2011-11-25
  • Contact: ZHOU Xiao-Guo E-mail:xzhou@ustc.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (10979042, 21073173) and National Key Basic Research Program of China (973) (2007CB815204).

摘要: 利用阈值光电子-光离子符合飞行时间质谱研究了氯甲烷分子在13至17 eV激发能量范围内的光电离和光解离动力学. 在此能量范围内, 电离产生的CH3Cl+离子处于A2A1B2E电子激发态. 两电子态均为完全解离态, 可生成CH3+和CH2Cl+碎片离子, 其中CH3+是最主要的解离产物. 拟合CH3+离子的符合飞行时间质谱峰形,可以得到CH3Cl+离子解离过程中释放的平动能分布, 结果显示CH3Cl+离子A2A1态解离生成CH3+ 的过程接近直接解离机理, 而B2E态的解离过程则具有统计解离的特征. 此外, 结合理论计算的势能面信息, 我们推测在A2A1态出现的CH2Cl+碎片离子来源于CH3Cl 分子自电离产生高振动激发的CH3Cl+(X2E)离子统计解离过程.

关键词: 氯甲烷, 光电离, 光解离, 飞行时间质谱, 势能面

Abstract: Using threshold photoelectron-photoion coincidence time-of-flight mass spectrometry, the photoionization and photodissociation of methyl chloride in the excitation energy range of 13-17 eV were investigated. CH3Cl+ ions in the A2A1 and B2E excited states were generated, both of which were completely dissociative. CH3+ fragments were mainly produced while CH2Cl+ fragment ions were observed as well. By fitting the time-of-flight profile the kinetic energy released distributions of CH3+ during the dissociation of the energy-selected CH3Cl+ ions were obtained. The dissociation of the CH3Cl+ (A2A1) ion followed rapid direct fragmentation while that of the B2E state showed statistical dissociation. Moreover, with the aid of the calculated potential energy surface the CH2Cl + fragment ions observed in the A2A1 state were generated from the statistical dissociation of the high vibrational excited CH3Cl+ (X2E) ions produced by the autoionization of the CH3Cl molecule.

Key words: Methyl chloride, Photoionization, Photodissociation, Time-of-flight mass spectroscopy, Potential energy surface

MSC2000: 

  • O643