Theoretical investigations of inelastic processes in slow to fast ion-atom collisions

Within the close-coupling formalism, we have studied the inelastic processes of a variety of ion-atom collision systems in a wide range of impact energies. Semiclassical approximation has been used for intermediate- to high-energy collisions. As for the low-energy collisions, quantum mechanical approach is applied.; We have performed an extensive semiclassical two-electron two-center atomic orbital close-coupling (TCAOCC2e) calculation to study the single ionization cross sections in p + He(1s2) collisions. The stabilities of the ionization probability and cross sections are examined with respect to the choice of the basis sets. Below 40 keV, our cross sections are slightly higher than the Force Impulse Method. They disagree with the existing experimental data, and therefore we conclude that a new measurement is needed.; A combination of the Eikonal approximation and a one-electron TCAOCC was utilized to study the state-selective differential charge transfer cross sections for Na+ + Rb(5s,5p) at E = 2, 5 and 7 keV. The theoretical results are in good agreement when compared to the recent measurements obtained with Rb targets cooled in a magnetic optical trap (MOTRIMS). Despite the fine resolution offered by MOTRIMS, the experimental angular differential cross sections do not exhibit the oscillatory structure shown in the theory.; Using the Hyperspherical method, we searched for bound rotational states of helium trimer by solving the Schrödinger equation in the adiabatic representation. From the resulting repulsive potential curves for non-zero angular momenta, we showed that there are no bound rotational states in any of the isotopes of the He trimer.; A conjoint technique of Hyperspherical Coordinate, Smooth Variable Discretization (SVD) and $R$-matrix propagation methods was used to study the slow 20 eV–2 keV H+ + D(1s) collisions. This quantum mechanical approach is free from ambiguities associated with the conventional Born-Oppenheimer (BO) method. We showed that the cross sections for excitation and charge transfer to 2p states are essentially identical over the whole energy range and stay relatively independent of energy from 2 keV down to 150 eV. Below 150 keV, the cross sections decrease precipitously with decreasing energy. The rapid drop of cross sections was explained with the aid of hyperspherical potential curves.