Theoretical study of electron-impact excitation of H(1s) into the n <= 4 states using a two-dimensional R-matrix propagator

Electron-impact excitation of the ground state of hydrogen into the n less than or equal to 4 stales is studied by propagating the R-matrix in the two radial dimensions. Integral cross sections and resonance parameters are pr esented for collision energies from 0.75 Ryd (the n = 2 threshold) up to 0. 96 Ryd (the n = 5 threshold). Below the n = 3 threshold, there is very good agreement with results from other methods and with experimental data. Betw een the n = 3 and n = 4 thresholds, integral cross sections are in better a greement with those of a coupled pseudostate method than with those of the J-matrix method, while resonance parameters are in good agreement with thos e of a 15-state R-matrix calculation.