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

Differential cross sections are calculated for the electron impact exc itation of 1(1)S-2(3)S transitions in helium at incident energies of 1 00 and 200 eV. A distorted wave approximation is used with the effect of target polarization taken into account. The results are compared wi th the recent experimental data of Sakai et al and with the recent R-m atrix method calculation of Nakazaki et al. The present cross section is in general agreement with the R-matrix calculation. It is found, ho wever, that the present calculation cannot reproduce the very large cr oss section obtained by Sakai et al in the forward direction at 200 eV .