| Atoms, moleculae or radicals can be excited to rovibratiofral levels of the selected states by the absorption of n-laser photons, then the parent ion can be produced by the absorption of another m-laser photons. Compared with the non-resonant absorption, the ion signal intensity of resonant absorption can be increased drastically due to resonant absorption between the intermidate state and the lower state, which being used as the basis to record the REMPI (Resonance Enhanced Multiphoton lonization) spectrum.ln noting that ion yield is dependent on rovibrational levels in the neutral excited state, the spectrum recorded is thus characteristic of this state. REMPI technique plays an important role in detecting high energetic excited electronic states of atoms, molecules and radicals. In particular, when the higher power laser is used as excited resource, we can detect high energetic excited electronic states or Rydberg states of molecules and radicals, and can obtain the signal better. Besides, we can select the special quanta states of molecules and radicals due to the coherence of the laser. Because of this, not only REMPI technique has been developed quickly, but also its application has been extensively enlarged. For example, it can be used to study the spectroscopy of high excited electronic states of molecules and radicals, photodissociation or photoionization dynamics, single atom detection, laser isotope separation, combustion diagnose and electronical vibrationalenergy transfer. No matter in basic field or in applied field, the study of REMPI and MPI in different systems has comprehensively scientific values and large scope for future applications.In recent years, the photodissociation of chloride and bromide has attracted much attention because these species play a key role in the depletion of the stratospheric ozone. It is said that the active bromine and chlorine in stratosphere mainly comes from photodissociation of chloride and bromide, and the active bromine and chlorine is an important factor in stratospheric ozone depletion. So photodissociation dynamics of chloride and bromide is very important in study of stratospheric ozone depletion. In this paper, using REMPI-TOF technique, multiphoton dissociation/ionization dynamics of dichloromethane and methyl bromide has been carried out. The mechanism of multiphoton dissociation/ionization has also been discussed, and obtained some valuable results. This essay is divided for five chapters. The main contents are listed as following.In chapter one, the MPI technique and its development, background, character and applied fields are presented. In chapter two, the basic principles of MPI technique are introduced including the selected rules, Rydberg states etc. In chapter three, the REMPI-TOF-MS equipment and the experimental method are introduced. In chapter four, theREMPI-TOF-MS of methyl bromide are investigated in the Wavelength range between 279.5-287nm. The main results are : (1) The T0F-MS of methyl bromide are identified. (2) The possible mechanism of dissociation/ionization is also discussed. (3) Four REMPI spectrum are identified. They are the spectrum of C and CH3. (4) Two forbidden transition spectrum of Br are found for the first time, which had been identified as (5) The formation of clusters found in our experiment is analyzed. It is proposed that the main dissociation channel is non-resonant photodissociation of parent molecule , followed by the further photodissociation or photoionization of the fragments. In chapter five, the spectrum of dichloromethane are investigated. (1) The TOF-MS of dichloromethane are identified. (2) The possible mechanism of dissociation/ionization is analyzed. (3) It is also proposed that the main dissociation channel is non-resonant photodissociation of parent molecule followed by the further photodissociation or photoionization of the fragments.
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