Chem. J. Chinese Universities ›› 2010, Vol. 31 ›› Issue (2): 367.

• Articles • Previous Articles     Next Articles

Ionization and Dissociation of Methyl Bromide in Intense Laser Field

YANG Zheng1, LIU Hong-Tao1, TANG Zi-Chao2, GAO Zhen1*   

  1. 1. State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China;
    2. State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
  • Received:2009-03-17 Online:2010-02-10 Published:2010-02-10
  • Contact: GAO Zhen. E-mail: gaoz@iccas.ac.cn
  • Supported by:

    国家自然科学基金(批准号: 20203020, 20433080)资助.

Abstract:

Ionization-dissociation of methyl bromide in intense laser field was studied using home-built reflection time-of-flight mass spectrometer. Based on the relative high resolution of the RTOF-MS(MM>2000), the Kinetic Energy Release(KER) of the fragment ions was measured. Multiphoton dissociation and Coulomb explosion mechanisms were used to explain the experimental results. Comparing with the result of methyl iodide in intense laser field, some differences are observed: (1) at the same laser field intensity, the highest charged fragment ion of methyl bromide was Br3+, lower than I6+ of methyl iodide; (2) the dehydrogenation channel was observed in the multiphoton dissociation or Coulomb explosion of methyl bromide, but was not observed in the case of methyl iodide; (3) HBr+ was observed, but there was no similar channel in the case of methyl iodide; (4) for methyl bromide, the valid charge distance of Coulomb explosion increases with the product of p and q; while in the case of methyl iodide, the distance remained almost the same; (5) the producing channel of CHm+(m=0, 1, 2) is different from the ionization-dissociation of methyl iodide in which the stepwise dissociation of CH3+ was thought to be the main channel, CHm+(m=0, 1, 2) of methyl bromide are mainly from the products of the direct dissociation of the dehydrogenated parent ions instead of the stepwise dissociation of CH3+.

Key words: Time-of-flight mass spectrometry; Intense laser field; Coulomb explosion; Multiphoton dissociation

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