Single charge exchange in fast collisions of alpha particles with helium

A new second-order theory termed the Born distorted wave (BDW) approximation is introduced within the framework of the four-body scattering theory and applied to single charge exchange in fast symmetric collisions between alpha particles and helium. The present formulation allows us to isolate the role of intermediate electron continuum states. At the intermediate projectile energies, the present BDW approximation represents a substantial improvement over the continuum distorted-wave four-body formulation, thus illustrating a remarkable sensitivity of second-order theories for single charge exchange to the treatment of electronic ionization continua. Numerical results for the total cross sections show a good agreement with the available experimental data.