Electron-impact excitation of helium from the 1 1S and 2 3S states

The R-matrix with pseudo-states (RMPS) method has been used to study electron-impact excitation of helium from the ground state (1s(2))S-1 and the metastable (1s2s)S-3 state for total energies up to 40 eV. The overall agreement with recent convergent close-coupling (CCC) calculations of Fursa and Pray is very satisfactory. The remaining disagreements are apparently associated with differences in the description of the target structure, which is superior in the present work compared to the frozen-core approach used in the CCC calculation. Severe discrepancies remain between the RMPS/CCC predictions and some experimental data, particularly for excitation from the 2(3)S state.