Integrated cross sections for the ionization of atomic hydrogen by electron impact

Distorted-wave Born approximation (DWBA) calculations are reported for singly differential and total cross sections for the electron impact ionization for atomic hydrogen at 25, 40, 60, 100, 150 and 250 eV. The theory is compared with available experiments. It predicts a less rapid decrease of the singly differential cross section with increasing secondary-electron energy than the absolute measurements of a previous author. Two different DWBA calculations are performed. The first approximation omits the post-collision interaction and the second one approximates it. The total ionization cross section in the second approximation agrees better in general with the shape of the experimentally measured cross sections. (Author)