Charge transfer and ionisation in collisions of 2.5 to 9 MeV protons with argon

We report theoretical ionisation and charge-transfer cross sections for p + Ar collisions in the 2.5-9 MeV energy range. The calculations employ large target-centred basis expansions of the scattering wavefunction, and are carried out in the method we have developed previously for K-shell ionisation and recently extended to charge transfer. Cross sections are presented for ionisation from the K shell and for electron capture from both the K and L shells of the target. These cross sections are all produced simultaneously in our calculational scheme. We compare our cross sections to the experiments of Macdonald et a/ and to the calculations of Lin et a1 and Lapicki and Losonsky. For K-shell capture and ionisation our results are in fairly good agreement with experiment; for L-shell capture they are larger than experiment by about a factor of two. We give evidence for the convergence of our calculations with respect to enlargements of the basis. We also discuss possible future refinements of the calculation, particularly with regard to the manner in which the independent-particle model is being employed.