Electron impact induced transitions between the n=1,2,3 levels of atomic hydrogen at low energies

An algebraic variational close-coupling code is used to evaluate electron impact excitation cross sections between the n=1, 2 and 3 levels of atomic hydrogen at energies up to the n=4 threshold. Results are obtained in a six-state basis and with a much larger basis (14 to 18 states). Comparisons are made with earlier six-state calculations. The results from the best basis are significantly lower than the previous six-state calculations for the 2l-3l' cross sections: in particular for 2p-3d they are more than a factor of two lower close to the n=3 threshold. The total n=2 to n=3 cross section is 76% lower than that of Burke and co-workers (1967) at the lowest energy. The positions and widths of the Feshbach resonances for L=0,1, in general, agree well with those of Ho (1979). There is a broad shape resonance ( 3 S) just above the n=3 threshold.