| The ionization-dissociation of methyl iodide in intense laser field has been studied using a time-of-flight mass spectrometry in the past decades. At a intensity of 1015w/cm2,the laser wavelength of 800nm and a pulse width 100fs, we observed the mass spectra of CH3I irradiated by ths femtosecond laser which consisted of the highly charged ions of iodide and carbon, and also found CH22+,CH3I2+. The obtained mass spectra of methyl iodide was different from others when coulomb explosion happened. We didn`t found the parent fragments when the laser intensity is strong and the anisotropic angular distribution of ion C2+ was also been observed.Berstein et al showed that when the single-photon excitation reached the dissociative A band ,then the methyl iodide was broken to produce CH3 and I fragments and they didn`t find the parent ions at wavelength of 266-307nm .Bobin et al studied the multiphoton ionization of methyl iodide for the wavelength of 530-710nm and its frequency multiplication band .Liu Songhao et al studied the photodissociation of CH3I at a wavelength of 308nm, they observed the fragments ions of CH3+,I+ and CH3I+ and indicated the existence of two ion channel which were the ionization of parent ion dissociation neutral fragments and the parent ion dissociation. Dobber et al applied the resonance multiphoton ionization and photoelectron spectroscopy method to study the Rydberg states in the nanosecond and picosecond pulsed laser field.At the low laser intensity, the parent ion peak was clearly recorded. The observed multi- charged molecular ions as In+ and Cp+ both had complex peaks which were also observed by P.Graham and Castleman and assigned to the Coulomb explosion of multi-charged molecular ions. But the peak profiles also presented in C.Kosmidis'experiments at lower laser intensities with picosecond and nanosecond laser pulses, the complex mass spectroscopy may be induced by the obverse and reverse detected ions. So the further confirm of ionization needed the distribution of momentum. We have calculated time difference of the fragments ejected to the backward and forward direction to detector and obtained the instantaneous kinetic energy(Ekin) of dissociated parent ion by the peak-separate method. The kinetic energy values of I ions increased as their charge values increase, which implied that the higher charged I ions weren't derived of the lower charged ones by further excitation ejected from the parent ion. Therefore, the Coulomb explosion mechanism within a multiple charged unstable parent ion should be invoked in our experiments.By rotating the half-wave plate, we could change the linear polarization vector of the laser beam relative to the TOF axis. Thus, we could obtained the angular distribution of the ion by meaning the ion intensity at different laser polarization angle. The angular distribution is isotropy and anisotropy. The anisotropic angular distrbutions of exploding fragments were attributed to dynamic or geometric alignment mechanisms. In the present study, the strong anisotropic angular distribution of the ions was observed, and it was different from the result of P Graham which in the intensity of 1016w/cm2.In the existing experimental conditions, our obtained mass spectra was different from the other literature. The reason was parent ions didn't appear in high intensity. Through the measurement of the angular distribution is strong anisotropic angular distribution. Analysis of anisotropic angular distribution of literature by different results. The experiment also parent ion angular distribution is not strong isotropic angular distribution. Along with the improvement of conditions in these areas need further proof.
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