Differential cross sections of helium for 11S-23S, 23P by electron impact at 100 and 200 eV

The R-matrix method is used to calculate differential cross sections for the transitions 1 1 S to 2 3 S and 2 3 P in helium by electron impact at incident energies 100 and 200 eV. An 11-state and a polarized pseudo-state calculation are performed. Present results are compared with the experimental results of Sakai et al. (1990) for the transition 1 1 S-2 3 S and with theoretical results of Fon et al. (1979) who included five states in an R-matrix calculation. It is seen that the present theoretical calculations for 1 1 S-2 3 S at 200 eV do not fully reproduce the large cross sections found at low angles in the experiments, although the present results are in good agreement with those at large angles.