DIFFERENTIAL CROSS-SECTIONS FOR ELECTRON-IMPACT 1(1)S-2(3)S EXCITATION IN HELIUM

Differential cross sections are calculated for the electron impact excitation of 1(1)S-2(3)S transitions in helium at incident energies of 100 and 200 eV. A distorted wave approximation is used with the effect of target polarization taken into account. The results are compared with the recent experimental data of Sakai et al and with the recent R-matrix method calculation of Nakazaki et al. The present cross section is in general agreement with the R-matrix calculation. It is found, however, that the present calculation cannot reproduce the very large cross section obtained by Sakai et al in the forward direction at 200 eV.