物理化学学报 >> 2011, Vol. 27 >> Issue (04): 965-970.doi: 10.3866/PKU.WHXB20110404

光化学和辐射化学 上一篇    下一篇

氯苯分子第一激发态超快动力学

刘玉柱, 秦朝朝, 张嵩, 王艳梅, 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:2010-12-16 修回日期:2011-01-21 发布日期:2011-03-29
  • 通讯作者: 张冰 E-mail:bzhang@wipm.ac.cn
  • 基金资助:

    国家自然科学基金(20973194)和中国科学院创新基金(KJCX1-YW-N30)资助项目

Ultrafast Dynamics of the First Excited State of Chlorobenzene

LIU Yu-Zhu, QIN Chao-Chao, ZHANG Song, WANG Yan-Mei, 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 Chinese Academy of Sciences, Beijing 100049, P. R. China
  • Received:2010-12-16 Revised:2011-01-21 Published:2011-03-29
  • Contact: ZHANG Bing E-mail:bzhang@wipm.ac.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (20973194) and Innovation Foundation of Chinese Academy of Sciences (KJCX1-YW-N30).

摘要:

利用时间分辨飞秒光电子影像技术结合时间分辨质谱技术, 研究了氯苯分子第一激发态的超快过程. 266.7 nm单光子将氯苯分子激发至第一激发态. 母体离子时间变化曲线包括了不同的双指数曲线. 一个是时间常数为(152±3) fs的快速组分, 另一个是时间常数为(749±21) ps的慢速组分. 通过时间分辨的光电子影像得到了时间分辨的光电子动能分布和角度分布. 时间常数为(152±3) fs的快速组分反映了第一激发态内部的能量转移过程, 这个过程归属为氯苯分子第一激发态耗散型振动驰豫过程. 时间常数为(749±21) ps的慢速组分反映了第一激发态的慢速内转换过程. 另外, 实验实时观察到典型的非对称陀螺分子(氯苯)激发态的非绝热准直和转动退相干现象. 并推算出第一次转动恢复时间为205.8 ps (C类型)和359.3 ps (J类型).

关键词: 光电子影像, 超快过程, 振动能量驰豫, 氯苯, 非绝热准直

Abstract:

Ultrafast dynamics of the first excited state (S1) of chlorobenzene was studied using a combination of femtosecond time-resolved photoelectron imaging and time-resolved mass spectroscopy. One-photon absorption at 266.7 nm was used to populate the S1 state of chlorobenzene. The time evolution of the parent ion signals consists of different biexponential decays. One is a fast component on a timescale of (152±3) fs and the other is a slow component with a timescale of (749±21) ps. Time- resolved electron kinetic energies (eKE) and time-resolved photoelectron angular distributions (PADs) were extracted from time-resolved photoelectron imaging and are discussed in detail. The ultrafast process with a time constant of (152±3) fs is a population transfer within the S1 state, and only a vibrational energy transfer process with strong coupling is a reasonable explanation. This is attributed to an ultrafast process of dissipative intramolecular vibrational energy redistribution (IVR). The lifetime of the S1 state was determined to be (749±21) ps, and its deactivation was due to slow internal conversion to the ground state. Additionally, nonadiabatic alignment and rotational dephasing of the S1 state of chlorobenzene, as a typical asymmetric top molecule, were observed. The first C-type and J-type recurrences are expected at delay time of 205.8 and 359.3 ps, respectively.

Key words: Photoelectron image, Ultrafast process, Vibrational energy redistribution, Chlorobenzene, Nonadiabatic alignment

MSC2000: 

  • O644