LASER-ASSISTED ELASTIC ELECTRON-ATOM COLLISIONS - LOW ELECTRON-ENERGYAND SMALL SCATTERING ANGLE

We report experimental measurements of electron spectra resulting from the scattering of low energy (6.2-32 eV) electrons by helium atoms th rough an angle of 9-degrees in the presence of a high intensity (appro ximately 10(8) W cm-2) CO2 laser. The intensities of the additional pe aks caused by the presence of the laser which occur separated from the elastic scattering peak by multiples of the photon energy are much gr eater than expected on the basis of calculations, using the Kroll-Wats on approximation. The intensity of these free-free transitions also in creases with decreasing electron energy, again in disagreement with th e calculations. We propose that the disagreement between our experimen tal results and those calculated is due to the electrons scattering fr om a helium target polarized by the laser field.