Laser-assisted single and double ionization of helium by electron impact

We consider theoretically laser-assisted ionization of a helium atom by electron impact at large momentum transfer. Fully differential cross sections of these processes are studied as functions of the recoil-ion momentum for the cases when the residual He + ion is left both in the bound ( n = 1 and n = 2) and in the continuum states in the presence of a linearly-polarized laser field with frequency w = 1.55 eV and intensity I = 5×10 11 W/cm 2 . We inspect how the orientation of the polarization influences the laser-assisted momentum profiles using different models of the helium wave function. It is found that the Kroll-Watson sum rule is well applicable in the ( e , 3 − 1 e ) case.