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CH_3I multiphoton ionization of molecular dissociation research

Author: LiLi
Tutor: KongXiangHe
School: Qufu Normal University
Course: Physical Electronics
Keywords: Iodomethane Multiphoton ionization Time-of-flight mass spectrometry Rydberg states
CLC: O621.1
Type: Master's thesis
Year: 2007
Downloads: 38
Quote: 1
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Abstract


Methyl iodide in the past few decades, is a widely studied molecule, methyl iodide photolysis channel not only closely related to the practical purpose of the development of chemical laser, but some basic theoretical issues reveals single-molecule photolysis process is very important significance. Methyl iodide is a relatively simple molecular structure to have C 3v symmetry, but it is also a very representative molecule, its rotation period is far greater than its dissociation time, therefore a detailed study of the methyl iodide molecule multiphoton ionization dissociation mechanism of polyatomic molecular dynamics characterization similar process obviously. In this paper, a time-of-flight mass spectrometer iodomethane Supersonic Jet cooling technology multiphoton ionization dissociation mechanism. Analysis by mass spectrometry under different laser wavelengths, 266nm laser effect, iodomethane experienced the neutral fragments photoionization process: methyl iodide absorption of a photon excitation to the exclusion of state A state rapid dissociation sexual debris CH 3 group and I atoms, CH , 3 group and I atoms has undergone a (21) multiphoton ionization process of the formation of the fragment ions CH 3 ions and I ions. In 355nm laser effect, multiphoton ionization of methyl iodide molecule dissociation (MPID) is a parent ion ladder mode: methyl iodide molecules by two-photon resonant excitation to Rydberg C state in the excited states of the parent molecule absorb photons pumped to the ionization state the parent ions CH 3 I , the base state parent ion CH 3 I re-absorption of a photon pumped to the ion excited state to generate fragment ions CH 3 and I . Combined with the parent ion and fragment ion appearance potential of multi-photon ionization of CH 3 I molecule dissociation channel analysis, the possible dissociation-ionization channel. 532nm laser effect, the ionization mechanism of methyl iodide molecule contains both parent ion ladder mode also contains the the neutral debris photoionization mode, methyl iodide molecule is not only experienced a parent ion dissociation process. The different role of different wavelengths of laser mass spectrometry. To better exposition of multiphoton ionization of iodomethane solution from the mechanism in three specific laser wavelength, were fixed laser relative pulse valve delay changing the laser energy range of ion mass spectrometry combined with ion signal intensity changes with the laser intensity single point maps, in the role of different wavelengths of laser multiphoton ionization of methyl iodide dissociation mechanism carried out a detailed analysis.

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CLC: > Mathematical sciences and chemical > Chemistry > Organic Chemistry > Organic Chemistry general issues > Theory of organic chemistry,physical organic chemistry
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