Comparison of convergent electron - hydrogen calculations

Integrated cross sections for the n = 1 and 2 states of atomic hydrogen are calculated by the convergent-close-coupling method for a range of closely spaced energies just above the n = 2 threshold. The cross sections are compared with those calculated by a pseudo-state calculation, and two other methods that also converge, in principle, to the exact result. These are the intermediate-energy R-matrix method and the convergent J-matrix method. Experimental data are described very well by all of these theories.