物理化学学报 >> 2009, Vol. 25 >> Issue (03): 423-429.doi: 10.3866/PKU.WHXB20090305

研究论文 上一篇    下一篇

邻溴甲苯在234和267 nm的光解动力学

曹振洲 张昌华 王艳梅 张锋 华林强 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:2008-10-07 修回日期:2008-11-25 发布日期:2009-03-02
  • 通讯作者: 张冰 E-mail:BZhang@wipm.ac.cn

Photodissociation Dynamics of o-Bromotoluene at 234 and 267 nm

CAO Zhen-Zhou, ZHANG Chang-Hua, WANG Yan-Mei, ZHANG Feng, HUA Lin-Qiang, 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 School of the Chinese Academy of Sciences, Beijing 100049, P. R. China
  • Received:2008-10-07 Revised:2008-11-25 Published:2009-03-02
  • Contact: ZHANG Bing E-mail:BZhang@wipm.ac.cn

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摘要：

利用离子速度影像技术结合共振增强多光子电离(REMPI)技术, 研究了邻溴甲苯在234和267 nm激光作用下的光解机理. 平动能分布表明, 基态Br(2P3/2)和自旋轨道激发态Br*(2P1/2)产生于两个解离通道: 快通道和慢通道. 快通道的各向异性参数在234 nm分别为1.15(Br)和0.55(Br*), 在267 nm分别为0.90(Br)和0.60(Br*). 慢通道的各向异性参数在234 nm分别为0.12(Br)和0.14(Br*), 在267 nm分别为0.11(Br)和0.10(Br*). 源自于慢通道的Br和Br*碎片的各向异性弱于快通道. Br(2P3/2)的相对量子产率Φ(Br)在234 nm为0.67, 在267 nm为0.70. 邻溴甲苯在234 和267 nm光解主要产生基态产物Br(2P3/2). 快通道产生于(π, π*)束缚单重态被激发, 随后通过排斥性(n, σ*)态的预解离. 慢通道各向异性参数接近零, 由此证实慢通道来源于单重激发态内转换到高振动基态而引发的热解离.

关键词: 离子速度影像, 光解离, 邻溴甲苯

Abstract:

The photodissociation of o-bromotoluene was studied at 234 and 267 nm using velocity map imaging combined with a resonance-enhanced multiphoton ionization (REMPI) technique. Translational energy distributions suggested that ground state Br(2P3/2) and spin-orbit excited state Br*(2P1/2) fragments were all generated via two dissociation channels: a fast channel and a slow channel. The anisotropy parameters of the fast channels were determined to be 1.15 (Br) and 0.55 (Br*) at 234 nm, 0.90 (Br) and 0.60 (Br*) at 267 nm. The anisotropy parameters of the slowchannels were 0.12 (Br) and 0.14 (Br*) at 234 nm, 0.11 (Br) and 0.10 (Br*) at 267 nm. The Br and Br*fragments of the slow channel were less anisotropic than those of the fast channel. The total relative quantumyields of Br (Φ(Br)) were 0.67 at 234 nm and 0.70 at 267 nm. Ground state Br(2P3/2) was the main product fromthe photolysis of o-bromotoluene at 234 and 267 nm. We propose that the fast channel originates from excitation of bound excited singlet (π, π*) states followed by predissociation along repulsive (n,σ*) states. The anisotropy parameters of the slowchannelswere close to zero indicating a hot dissociation mechanism on a highly vibrational ground state followed the internal conversion of the excited singlet state.

Key words: Ion velocity imaging, Photodissociation, o-Bromotoluene