Low-energy electron-He scattering in a low-frequency laser field

A method for calculating the laser-assisted, electron-potential scattering differential cross section that is based on the Floquet-Lippmann-Schwinger equation is presented. The method is applied to the laser-assisted, low-ene rgy electron-helium scattering in a CO2 laser field, in the static no-excha nge approximation, for the scattering geometry in which the polarization ve ctor of the laser field is parallel to the direction of the incident electr on. We compare our results with the low-frequency approximation of Kroll an d Watson [Phys. Rev. A 8, 804 (1973)] and find, overall, reasonable agreeme nt. An alternative derivation of the Kroll and Watson low-frequency approxi mation, starting from the Floquet-Lippmann-Schwinger equation, is given in an appendix. [S1050-2947(99)11208-3].