Electron angular distributions in above threshold ionization of xenon.

Angular distributions of the photoelectrons produced in above threshold ionization of xenon by 100 psec 1.06micron laser pulses have been measured. We find that the electron angular distributions, which are peaked along the polarization direction for linearly polarized light, differ for electrons emitted with different kinetic energies, corresponding to the absorption of different numbers of photons. Furthermore, for a given electron energy, the angular distribution is strongly dependent on the laser intensity. We propose that ponderomotive potential scattering is mainly responsible for the intensity dependence of the angular distributions.