Laser-assisted (e,3e) collisions in helium at high impact energy and large momentum transfer

Electron-impact double ionization of a helium atom in the presence of laser radiation with low frequency and intensity is studied theoretically. The kinematical regime of high impact energy and large momentum transfer, with one slow and two fast electrons in the final channel, is considered. Fully differential cross sections corresponding to the laser-assisted (e,3e) and (e,3 - 1e) processes are calculated for different models of the target state. The angular distributions of the slow ejected electron are found to be seriously modified by the laser field and, in contrast to the field-free case, are strongly dependent on the electron-electron correlations in helium. At the same time, the laser-assisted (e,3 - 1e) results very slightly differ from those in the absence of a laser field.