Electron-helium scattering in a 1.17 eV laser field: The effect of polarization direction

Abstract

We report measurements of one-photon emission during the elastic scattering of electrons by He atoms through ${90}^{\ensuremath{\circ}}$ in the presence of 1.17 eV photons from a Nd:YAG laser. The incident energy of the electrons was in the range 30--200 eV and the linear polarization direction of the laser was varied over ${180}^{\ensuremath{\circ}}$ in the plane, perpendicular to the scattering plane, that contains the momentum transfer direction. Our results are perfectly consistent with the Kroll-Watson approximation. In particular, we see no evidence of free-free transitions when the polarization is perpendicular to the momentum transfer direction.