Laser-assisted electron-helium scattering at very low collision energies

The R-matrix Floquet theory is used to study laser-assisted electron-helium scattering in the energy range from 0.2 to 2.5 eV. Differential cross sections and signals for scattering through 156 degrees in a CO2 laser field are calculated over a range of intensities from 10(6) to 10(8) W cm(-2) and compared with those obtained experimentally. Similar calculations for scattering in a Nd:YAG laser field are also presented in order to assess the validity of the Kroll-Watson low-frequency approximation when the scattering energy is less than the photon energy.