Indirect coupling mechanisms and Stokes parameters for electron-atom scattering

The predictions of the multichannel eikonal theory (MET) and two distorted wave theories are considered for the sigma 11S not=31D integral cross section and the Stoke parameters P i (i=1,2,3) for the 3 1 D state of He at intermediate energies. Significant differences are found between the distorted wave and multichannel eikonal theories for the Stokes parameters in the case where the dipole couplings 2 1 P m to 3 1 D m' and 3 1 P m to 3 1 D m' are omitted in the solution of the coupled equations of the eikonal theory. Switching off the electric dipole transitions coupling the 2 1 P m and 3 1 P m states to the 3 1 D m' substates in the MET changes the underlying MET complex scattering amplitudes for the 3 1 D m' magnetic substates in such a way that the resultant sigma 11S not=31D integral cross section for the excitation of the 3 1 D state of He drops by a factor of between 5 and 8 for incident electron energies E between 30 and 60 eV.