Single and multiple electron removal processes (capture and ionization) in proton-H 2 O collisions have been investigated applying the continuum distorted wave with eikonal initial-state model within the framework of independent electron approach. Probabilities and cross sections for electron capture are derived from the same quantities evaluated for ionization using the continuity of transition quantities across the ionization threshold. Dissociation and fragmentation cross sections for the H 2 O q+ (q = 1-3) ions have been evaluated by considering branching ratios that include the effect of multiple electron removal transitions. The results are compared with experimental and other theoretical data in the range of impact energies from 30 kev to 5 MeV. Generally, the evaluated cross sections and fragmentation yields show good agreement with experiments at impact energies above 100-150 keV.

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A three-body Coulomb-Born continuum distorted-wave approximation is applied to calculate the differential and total cross sections for single-electron exchange in the collision of fast alpha particles with helium atoms in their ground states. The applied first-order distorted wave theory satisfies correct Coulomb boundary conditions. Both post and prior forms of the transition amplitude are calculated. The nuclear-screening effect of the passive electron on the differential and total cross sections is investigated. The results are compared with those of other theories and with the available experimental data. For differential cross sections, the comparisons show a reasonable agreement with empirical measurements at higher impact energies. The agreement between experimental data and the present calculations for total cross sections with the average of the post and prior forms of the transition amplitude is reasonable at all the specified energies.

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Both the post and prior versions of the four-body Coulomb–Born distorted wave (CBDW-4B) approximation are applied to calculate the single-electron capture differential and integral cross sections in collision of the fast protons with helium atoms. The outlined model satisfies the correct boundary conditions, and the incident energy is considered in a range of 20 to 1000 keV for which the applied approach is valid. For proton–helium collisions, the CBDW-4B method exactly coincides with the four-body first-order Jackson–Schiff approximation (JS1-4B). The influence of the static and dynamic electronic correlations on the cross sections is investigated. The ground state of the helium atom is described using two different wave functions to show the influence of the static correlation on the captured cross sections. In order to illustrate the validity of the present method, the obtained results are compared with the other theoretical investigations as well as the available experimental measurements. Although the overall agreement of the present numerical differential cross sections (DCS) with the reported experimental findings is acceptable, contrary to our general expectation, the three-body version of the formalism gives a better description of the angular distribution of the captured cross sections. However, for integral cross sections, the agreement of the four-body results with the reported measurements is better than those of three-body formalism.