物理化学学报 >> 2012, Vol. 28 >> Issue (03): 522522-527..doi: 10.3866/PKU.WHXB201201122

热力学,动力学和结构化学 上一篇    下一篇

丙烯酸分子的激发态超快预解离动力学

张蓉蓉, 秦朝朝, 龙金友, 杨明晖, 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:2011-11-23 修回日期:2011-12-29 发布日期:2012-02-23
  • 通讯作者: 张冰 E-mail:bzhang@wipm.ac.cn
  • 基金资助:

    国家自然科学基金(20903116)和中国科学院知识创新基金(KJCX1-YW-N30)资助项目

Ultrafast Predissociation Dynamics of Excited State of Acrylic Acid

ZHANG Rong-Rong, QIN Chao-Chao, LONG Jin-You, YANG Ming-Hui, 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:2011-11-23 Revised:2011-12-29 Published:2012-02-23
  • Contact: ZHANG Bing E-mail:bzhang@wipm.ac.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (20903116) and Knowledge Innovation Foundation of Chinese Academy of Science (KJCX1-YW-N30).

摘要: 利用飞秒泵浦-探测技术结合飞行时间质谱(TOF-MS), 研究了丙烯酸分子被200 nm泵浦光激发到第二电子激发态(S2)后的超快预解离动力学. 采集了母体离子和碎片离子的时间分辨质谱信号, 并利用动力学方程对时间分辨离子质谱信号进行拟合和分析, 揭示了预解离通道的存在. 布居在S2激发态的分子通过快速的内转换弛豫到第一电子激发态(S1), 时间常数为210 fs, 随后再经内转换从S1态弛豫到基态(S0)的高振动态, 时间常数为1.49 ps. 分子最终在基态高振动态势能面上发生C-C键和C-O键的断裂, 分别解离生成H2C=CH和HOCO、H2C=CHCO和OH中性碎片, 对应的预解离时间常数分别约为4 和3 ps. 碎片离子的产生有两个途径, 分别来自于母体离子的解离和基态高振动态势能面上中性碎片的电离.

关键词: 时间分辨质谱, 超快动力学, 泵浦-探测, 飞行时间质谱, 内转换

Abstract: The ultrafast predissociation dynamics of acrylic acid after excitation to the second electronically excited state (S2) with a 200 nm pump pulse were studied using a femtosecond pump-probe technique combined with time-of-flight mass spectroscopy (TOF-MS). The time-resolved mass spectra signals of the parent ion and fragment ions were collected. By using the kinetic equations to fit and analyze the time-resolved mass spectra ion signals, the existence of the predissociation channel was revealed. The excited molecule populated in the S2 state decayed to the first electronically excited state (S1) through a fast internal conversion process over a period of 210 fs. The excited molecule populated on the S1 state then decayed to the vibrationally hot ground state (S0) through another internal conversion process over a period of 1.49 ps. Finally, on the vibrationally hot ground state surface, the molecule dissociated to the neutral fragments, H2C=CH and HOCO, H2C=CHCO and OH via C-C bond fission and C-O bond fission, respectively. The corresponding predissociation time constants were determined to be approximately 4 and 3 ps, respectively. The generation of fragment ions can occur in two ways, both from the dissociation of the parent ion and the ionization of the neutral fragments on the vibrationally hot ground state surface.

Key words: Time-resolved mass spectrum, Ultrafast dynamics, Pump-probe, Time-of-flight mass spectroscopy, Internal conversion

MSC2000: 

  • O644