A 29-STATE R-MATRIX INVESTIGATION OF RESONANCES IN E--HE SCATTERING AT LOW ENERGIES .1. ON THE CONVERGENCE OF THE CALCULATIONS OF (1)S-2(3.1)S EXCITATION CROSS-SECTIONS

Fon and Lim have reported the 11-state and the 19-state R-matrix calculations of 1(1)S-2(3)S differential cross sections at low energies. The discrepancy between the R-matrix calculations at scattering angle 90-degrees and the experiments remains at 20%. Another attempt has been made here to reduce the discrepancy. Recently Sawey et al reported a 29-state R-matrix calculation on the collision strengths for the 1(1)S-2(3,1)S excitation, and an error in their representation of the 19-state collision strengths, which were wrongly shown to be significantly higher than the 29-state results, is corrected. In this paper, the same 29-state R-matrix calculation of Sawey et al is extended to obtain 1(1)S-2(3,1)S excitation cross sections at 500 energies ranging from the 2(3)S threshold to 24.2 eV for scattering angles 30-degrees, 55-degrees, 60-degrees, 90-degrees, 120-degrees, 125-degrees and 140-degrees. The convergence of the R-matrix calculations in shape and magnitude of the cross sections is re-examined.