TRIPLY DIFFERENTIAL CROSS-SECTIONS FOR IONIZATION OF HYDROGEN-ATOMS BY ELECTRONS - THE INTERMEDIATE AND THRESHOLD ENERGY REGIONS

Triply differential cross sections in coplanar geometry for the ionization of atomic hydrogen by electron impact have been measured and calculated at incident electron energies of 54.4, 27.2, 17.6 and 15.6 eV. The theory is the same as that used successfully at higher energies and is shown to reproduce nearly all features of the cross sections in this low-energy regime as well. Moreover, the physical origin of peaks and dips in the triply differential cross sections has been explained. We conclude that kinematical effects, exchange effects, correlation and the coherence between electron-electron and electron-proton scattering are all important at these energies.