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Single-centred expansion coupled states calculations are performed with basis sets large enough to achieve convergence. The particular collision system studied is p+H(1s) at energies of 15 keV and above. The results obtained establish the validity of this method for calculating excitation and electron removal cross sections even in situations where charge transfer is large. Cross sections for 1s to 2l', 3l' and 4l' excitation and for electron removal are presented and compared to experiment and to other theoretical calculations.

Single-centred coupled states calculations of cross sections for excitation and ionization of atomic hydrogen by antiprotons are compared to previous calculations and to experiment for projectile energies in the range 1-300 keV. A noticeable disagreement between experiment and theory is found for the antiproton ionization results in the range 30-80 keV.

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Coupled-states calculations with large target-centred basis sets have been used to compute ionization probabilities and cross sections for at collision energies down to 10 keV. The results are in good agreement with recent theoretical calculations based on numerical solution of the time-dependent Schrödinger equation but there are no experimental data. Both an independent particle model and an independent event model were used to carry out calculations for . These results are in good agreement with experiment at 40 keV and above but differ at lower energies. The impact-parameter-dependent probabilities for these collisions were used in the independent event model to calculate helium double-ionization cross sections and excellent agreement was found with experimental measurements between 13 and 200 keV, but this simple way of treating correlation fails at higher collision energies.

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Our previous forced impulse method calculations of single and double ionization of helium by protons and antiprotons have been improved by including d orbitals in the target centred basis. The calculations are in good agreement with experimental measurements of the ratio R of double to single ionization, without the 1.35 scaling factor we applied to our previous results. We also compare the separate single and double ionization cross sections to experiment and find good agreement. Experimental cross sections differential in projectile scattering angle at large angle (greater than 2.5 mrad) are compared to our impact parameter dependent ionization probabilities at small impact parameter, for the double to single ratio. The agreement is good, except at the lowest energy we have considered, 0.3 MeV.