ABSTRACT
The impulse approximation (IA), originally proposed for short-range interactions, is well established in nuclear physics due to its sound principles and good agreement with experiments. Nevertheless, the IA ignores multiple scattering effects altogether. In addition, the binding target interactions are considered as unimportant, except for generating the momentum distribution of the initial electronic state. In atomic collisions, the IA is also one of the most frequently employed tools. The present numerical computations for the same process of electron capture from atomic hydrogen by proton impact show that the reformulated impulse approximation (RIA) is in excellent agreement with the available experimental data over a large interval of incident energies ranging from 20 to 7500 keV. Substantial improvements in the RIA over IA are also obtained for differential cross sections even at energies where Thomas double scattering becomes important. In atomic collisions, the IA is also one of the most frequently employed tools.
