Strong potential wave functions with elastic channel distortion

The strong-potential Born approximation is analyzed in a channel-distorted-wave approach. Channel-distorted SPB wave functions are reduced to a conventional form in which the standard off-energy-shell factor g has been replaced by a modified factor {γ}, which represents a suitable average of g over the momentum distribution of the distorted-channel function. The modified factor is evaluated in a physically realistic model for the distortion potential, and it is found that {γ} is well represented by a slowly varying phase factor. The channel-distorted SPB approximation is accordingly identical to the impulse approximation if the phase variation of {γ} can be ignored. This is generally the case in applications to radiative electron capture and to a good approximation for ordinary capture at not too small velocities.