Off-shell effects in three-body equations for the atomic reactions of electron transfer

Abstract

We have evaluated off-shell effects in three-body equations of the Alt-Grassberger-Sandhas type for electron-transfer reactions in ion-atomic collisions. The evaluation was made by an iteration method, that is, the contribution of principal value integrals was considered as a correction. Zero- and first-order results were compared. A pole graph was used as an effective potential in a charge-exchange channel. An evaluation of off-shell effects was made for two processes, namely, for H++H(1s) and He2++H(1s) collisions at energies 0.2-500 keV amu-1. In the case of the latter reaction the calculations were made without taking into account centre-of-mass Coulomb interaction between He+ and H+ ions in the final state. It was shown that in the resonant transition cases the off-shell effects are non-essential for all energies considered. For the partial cross sections of the non-resonant transfer, the off-shell effects might be essential at low and intermediate energies but their contribution approaches zero for higher energies. In the calculations of the total cross sections of the electron-transfer reactions the off-shell effects are non-essential for all energies considered.