Electron capture in collisions between protons and the ions He⁺and Li⁺,²⁺calculated using a new united-atom model

A new theoretical approach to calculate electron capture cross sections for ion-ion collisions in the intermediate energy region is developed. The impact parameter Schrodinger equation is solved by using an expansion in a two-state orthogonal basis which contains the charge Z(R) of the 'united atom'. The electron capture amplitude is expressed in an analytic form for low capture probabilities and the peak point approximation. The results for H + +He + and H + +Li + agree well with experimental data in the ranges 30-200 keV and 70-300 keV respectively. The results are compared with other theoretical results and quite a good agreement is obtained.