Role of the space charge in above-threshold ionization

A study was made of the influence of the space charge of a cloud of residual ions on the energy and angular distributions of electrons in the case of above-threshold optical ionization. This influence accounted for the characteristic reduction in the intensity of the first (with energies closest to the threshold ionization energy) peaks in the energy distribution of electrons. The mechanism of this influence could be electron trapping by the charged cloud of ions remaining in the interaction region. The space charge of the ions affected also the angular distribution of electrons escaping from the ionization region.