Wavepacket continuum-discretisation approach is used to calculate excitation, ionization and electron-capture (ec) cross sections for proton collisions with n=2 states of atomic hydrogen, where n is the principal quantum number. The approach assumes a classical motion for the projectile and is based on the solution of the three-body Schrödinger equation using the two-center expansion of the total scattering wave function. The scattering wave function is expanded in an orthonormal basis set built from negative-energy eigenstates and wavepacket pseudostates representing the continuum of both the target atom and the atom formed by the projectile after capturing the electron. With a sufficiently large basis, due to the strong coupling between channels, the method produces converged cross sections for direct-scattering, ionization and ec processes simultaneously. For the quasi-elastic transitions, where both orbital and magnetic quantum numbers change, the integrated cross section is infinite. Nevertheless, the corresponding transitions probabilities are finite at any given impact parameter, indicating that the angular differential cross sections can be measured. Calculated cross sections for scattering on the metastable 2s state are compared with other theoretical results obtained using atomic-orbital close-coupling and classicaltrajectory Monte Carlo approaches. Considerable disagreement with previous calculations has been found for some transitions at various incident energies.

The wave-packet convergent close-coupling method has been applied to model electron capture, excitation and ionization processes in He 2+ -H and H + -He + collisions. These processes constitute all possible reactions taking place in a three-body system of an α particle, a proton and an electron but corresponding to two different initial states. We present systematic and convergent calculations of nl-resolved cross sections required for plasma modeling and diagnostics. The presented results are largest and most accurate to date. The integrated cross sections for electron capture, excitation and ionization show generally good agreement with experimental measurements and previous close-coupling calculations where available, however the calculated cross section for Balmer-α emission in He 2+ -H collisions significantly disagree with experiment. We also present the fully differential, as well as various doubly and singly differential cross sections for ionization in He 2+ -H collisions at an incident energy of 200 keV amu −1 .

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Ionization and electron capture in collisions of bare carbon ions with atomic hydrogen has been studied using the wavepacket continuum discretization approach. The three-body Schrödinger equation governing the collision process is solved using the two-center expansion of the total scattering wavefunction. Calculations have been performed for the projectile energy range from 1 keV/amu to 10 MeV/amu. While there is excellent agreement with experimental data for the total electroncapture cross section over the entire energy range, the calculated total ionization cross section slightly overestimates the only available measured point. The singly and doubly differential ionization cross sections at 1 and 2.5 MeV/amu are in good agreement with experiment. The differential cross section calculations are extended to lower energies where perturbative methods are expected to fail. At 100 keV/amu impact energy the present singly differential cross section in the ejected angle of the electron shows a pronounced peak in the forward direction. It is concluded that at low incident energies electron capture into the continuum of the projectile strongly enhances electron ejection in the forward direction.

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