物理化学学报 >> 2009, Vol. 25 >> Issue (08): 1708-1712.doi: 10.3866/PKU.WHXB20090822

研究论文 上一篇    

氯碘甲烷在A带的光解动力学

张昌华, 张延, 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|中国科学院研究生院, 北京 100049
  • 收稿日期:2009-04-24 修回日期:2009-06-03 发布日期:2009-07-16
  • 通讯作者: 张冰 E-mail:bzhang@wipm.ac.cn

Photodissociation Dynamics of Chloroiodomethane in the A-Band

ZHANG Chang-Hua, ZHANG Yan, ZHANG Song, ZHANG Bing   

  1. State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, P. R. China|Graduate University of the Chinese Academy of Sciences, Beijing 100049, P. R. China
  • Received:2009-04-24 Revised:2009-06-03 Published:2009-07-16
  • Contact: ZHANG Bing E-mail:bzhang@wipm.ac.cn

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摘要：

利用离子速度影像方法结合共振增强多光子电离(REMPI)技术研究了氯碘甲烷在A带的光解机理. 从266和277 nm的I*(5p 2P1/2)和I(5p 2P3/2)离子速度影像获得了碎片的平动能分布和角度分布. I和I*的平动能分布呈单高斯型, 可用软自由基近似来解释. I和I*是在排斥的势能面上直接解离产生的. 实验得到的各向异性参数β证实分子受激发后主要产生3Q0态, 并且3Q0和1Q1态之间存在非绝热转移. 波长越短, 这种非绝热转移越强. 在235 nm附近, Cl和Cl*各向同性的离子影像说明氯原子来自于CH2ICl的二次解离过程, 即CH2ICl先解离产生CH2Cl自由基, 自由基再解离产生氯原子.

关键词: 光解离, 离子速度影像, 氯碘甲烷, 二次解离

Abstract:

The photodissociation dynamics of chloroiodomethane in the A-band has been investigated by ion velocity imaging coupled with a resonance enhanced multiphoton ionization (REMPI) scheme. Translational energies and angular distributions of the corresponding photofragments were obtained by detecting ion images of I*(5p 2P1/2) and I (5p 2P3/2) at 266 and 277 nm. Single-peaked Gaussian translational energy distributions were found for I and I* and could be interpreted in terms of the soft radical approximation. The formation of I and I* took place via a fast direct dissociation process on a repulsive potential energy surface. The obtained anisotropy parameter β proved that the existence of a nonadiabatic transition between the 3Q0 and 1Q1 states, and excitation at these wavelengths was predominated to the 3Q0 state. The nonadiabatic transition between the 3Q0 and 1Q1 states is stronger at shorter wavelengths. Around 235 nm, the isotropic Cl and Cl*ion images suggest that the observed chlorine atoms come from the secondary UV photodissociation of CH2Cl radicals which are initially produced by the photodissociation of CH2ICl.

Key words: Photodissociation, Ion velocity imaging, Chloroiodomethane, Secondary photodissociation process