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化学学报
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化学学报 ›› 2007, Vol. 65 ›› Issue (6): 501-508. 上一篇    下一篇

研究论文

离子速度成像方法研究二溴甲烷的紫外光解动力学

姬磊*,1,2, 唐颖2, 张冰2   

  1. (1大庆石油学院化学化工院 大庆 163318)
    (2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)
  • 投稿日期:2006-05-10 修回日期:2006-10-16 发布日期:2007-03-28
  • 通讯作者: 姬磊

Photodissociation Dynamics Study of CH2Br2 in Ultraviolet Region by the Ion-Velocity Imaging Technique

JI Lei*,1,2; TANG Ying2; ZHANG Bing2   

  1. (1 Chemistry and Chemical Engineering Institute, Daqing Petroleum Institute, Daqing 163318)
    (2 State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071)
  • Received:2006-05-10 Revised:2006-10-16 Published:2007-03-28
  • Contact: JI Lei

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利用二维离子速度成像(Ion-Velocity Imaging)方法对二溴甲烷分子在234和267 nm附近的光解动力学行为进行了研究. 实验中得到了二溴甲烷光解产生的Br*(2P1/2)和Br(2P3/2)在不同波长下的角度和平动能分布. 在平动能分布中发现两个高斯分布, 推测其中主要是C—Br的快速解离, 而高能宽分布则来自于CH2Br自由基的二次解离过程. 通过角度分布得到了Br*与Br中来自直接解离和非绝热交叉跃迁两种来源的比例. 结果表明Br*原子主要来自于B1态的直接解离, 而Br则绝大部分是从B1态向A1的非绝热交叉跃迁得到, 并导致了两种解离通道能量分布的差别.

关键词: 二溴甲烷, 光解动力学, 离子速度成像

The photodissociation dynamics of CH2Br2 was investigated near 234 and 267 nm. A two dimensional photofragment ion-velocity imaging technique coupled with a (2＋1) resonance-enhanced multiphoton (REMPI) ionization scheme was utilized to obtain the angular and translational energy distributions of the nascent Br(2P3/2) and Br*(2P1/2) atoms. The translational energy distributions of Br and Br* were found to consist of two components which should come from the radical channel and sec-ondary dissociation process, respectively. By analyzing the angular distributions, the fractions of the direct and non-adiabatic dissociation in the Br and Br* channels were obtained. It was suggested that Br* come from the direct dissociation of B1 state mostly, while Br atom be pro-duced by non-adiabatic transition between the B1 and A1 states. Consequently, the phenomena of the higher internal energy distribution of Br channel than that of Br* forma-tion channel and the broader translational energy distribution of the former can be explained well.

Key words: dibromoalkane, photodissociation dynamics, ion-velocity imaging