Laser-assisted elastic electron scattering from helium

We report measurements of the differential cross section for scattering of electrons, from helium, with energies in the range 1-20 eV through scatteri ng angles of 14 degrees -140 degrees in the presence of a high-intensity ca rbon dioxide laser. These results were obtained with beam geometries for wh ich the Kroll-Watson approximation, normally applied to these types of meas urements, predicts zero cross sections. The cross sections reported are not zero but confirm similar experiments with argon as the scattering centre.