Angular distribution anisotropy of fragments ejected from methyl iodide clusters: Dependence on fs laser intensity

The angular distribution of the fragment ions ejected from the interaction of methyl iodide clusters with 20 fs strong laser pulses is studied by means of a mass spectrometer. Three types of angular distributions, one isotropic and two anisotropic, have been observed and their dependence on the laser intensity has been studied. There is strong evidence that the ions exhibiting anisotropic angular distribution with a maximum in the direction parallel to the laser polarization vector are produced via an electron impact ionization process.