Electron-impact ionisation of atomic hydrogen from near threshold to high energies

Abstract

Application of the convergent close-coupling (CCC) method to electron-impact ionisation of the ground state of atomic hydrogen is considered at incident energies of 15·6, 17·6, 20, 25, 27·2, 30, 54·4, 150 and 250 eV. Total through to fully differential cross sections are presented. Following the analysis of Stelbovics (1999) the equal-energy sharing cross sections are calculated using a solely coherent combination of total-spin-dependent ionisation amplitudes, which are found to be simply a factor of two greater than the incoherent combination suggested by Bray and Fursa (1996). As a consequence, the CCC theory is particularly well-suited to the equal-energy-sharing kinematical region, where it is able to obtain convergent absolute scattering amplitudes, fully ab initio. This is consistent with the step-function hypothesis of Bray (1997), and indicates that at equal-energy-sharing the CCC amplitudes converge to half the step size. Comparison with experiment is satisfactory in some cases and substantial discrepancies are identified in others. The discrepancies are generally unpredictable and some internal inconsistencies in the experimental data are identified. Accordingly, new (e, 2e) measurements are requested.