On the choice of translation factors for approximate molecular wavefunctions

A critical analysis is presented for three different methods which introduce translation factors in the molecular approach to atomic collisions. Approximate one- and many-electron wavefunctions are explicitly considered. The charge exchange cross section for He2+ + H(1s) → He+(2s,2p) + H+ is used as illustration and shows a strong origin dependence in the standard perturbed stationary states (PSS) approach. The main conclusions are: (i) that the Bates-McCarroll method, and the method of projection on atomic components, are not necessarily convergent, and are time consuming for approximate wavefunctions and (ii) that the common translation factor method is the most promising approach at present. However, before it can be used systematically in molecular calculations, more research is needed regarding its sensitivity to the analytical form of the common factor. (author)