Signatures of laser photon energy in (e, 2e) reactions in helium

Electron-impact ionization of helium target in the presence of a linearly polarized laser field is investigated at low incoming energy in the second Born approximation and in the asymmetric coplanar geometry. The status of incident and scattered electrons in the external laser field is described by the non-relativistic Volkov waves. The dressed state of the ejected electron is treated as a Coulomb-Volkov wave function. The laser polarization vector is taken to be parallel to the incident momentum of the projectile. The scattering amplitudes are performed by using the Sturmian basis. Numerical results show that the laser photon energy dependence of the angular distributions of the ejected electrons has a significant control on the (e, 2e) reactions. The structure of the triple differential cross section in the vicinity of resonances have been discussed. The higher order terms of the Born series of the scattering amplitude will be negligible compared to the first terms at high laser frequencies.