Theoretical studies of the interaction of He²⁺with H(1s) and H⁺with He⁺

Cross sections calculated using an atomic basis are presented for the charge exchange reaction He 2+ +H(1s) to He + (nl)+H + for states with n<or=3. Excitation and ionisation cross sections for He 2+ impact on atomic hydrogen are calculated within a model using expansions into both atomic states and pseudostates. A two-centre expansion using the same basis is applied to the reaction H + +He + (1s) to H+He 2+ and results are obtained in harmony with experiment and with calculations using alternative basis sets.