Algebraic Treatment of Multistep Processes in Electron-Molecule Scattering

Abstract

The scattering of medium energy electrons from polar molecules is a complicated process involving many partial waves and the virtual excitation of many intermediate states [1]. For forward angles (θ< 60°) the scattering process is largely dominated by the long range dipole interaction between the incoming electron and the molecule. For large angles the scattering is more sensitive to short range features of the molecular dynamics, such as exchange correlations. For relatively small values of the dipole moment,d ≃1 Debye, the Born approximation already gives a good description of the experimental cross section. For strongly polar molecules the channel coupling between the rotational and vibrational degrees of freedom becomes increasingly important. This is illustrated in Figure 1, where the experimental cross section for electron scattering from LiF, which has a dipole moment of d = 6.58 Debye, is compared with the Born approximation. For very small angles the Born approximation is still adequate, but for larger angles multistep excitations have to be taken into account.