Charge exchange scattering amplitude to first order of a three body expansion

An analytical scattering amplitude for charge exchange processes is derived by means of a quantum three body theory for rearrangement collisions. This expression is the rigorous first order term of a perturbation series and should be useful in the intermediate and high energy range, say E>25 keV. It is equivalent to the continuum distorted wave approximation introduced by Cheshire by means of an impact parameter method.